diff --git a/assignment-client/src/avatars/AvatarMixer.cpp b/assignment-client/src/avatars/AvatarMixer.cpp
index 33e1034128..ffe084bc33 100644
--- a/assignment-client/src/avatars/AvatarMixer.cpp
+++ b/assignment-client/src/avatars/AvatarMixer.cpp
@@ -253,10 +253,26 @@ void AvatarMixer::start() {
 
         int lockWait, nodeTransform, functor;
 
+        // Set our query each frame
         {
             _entityViewer.queryOctree();
         }
 
+        // Dirty the hero status if there's been an entity change.
+        {
+            if (_dirtyHeroStatus) {
+                _dirtyHeroStatus = false;
+                nodeList->nestedEach([&](NodeList::const_iterator cbegin, NodeList::const_iterator cend) {
+                    std::for_each(cbegin, cend, [](const SharedNodePointer& node) {
+                        if (node->getType() == NodeType::Agent) {
+                            auto& avatar = static_cast<AvatarMixerClientData*>(node->getLinkedData())->getAvatar();
+                            avatar.setNeedsHeroCheck();
+                        }
+                    });
+                });
+            }
+        }
+
         // Allow nodes to process any pending/queued packets across our worker threads
         {
             auto start = usecTimestampNow();
@@ -973,19 +989,31 @@ void AvatarMixer::parseDomainServerSettings(const QJsonObject& domainSettings) {
     {
         const QString CONNECTION_RATE = "connection_rate";
         auto nodeList = DependencyManager::get<NodeList>();
-        auto defaultConnectionRate = nodeList->getMaxConnectionRate();
-        int connectionRate = avatarMixerGroupObject[CONNECTION_RATE].toInt((int)defaultConnectionRate);
-        nodeList->setMaxConnectionRate(connectionRate);
+        bool success;
+        int connectionRate = avatarMixerGroupObject[CONNECTION_RATE].toString().toInt(&success);
+        if (success) {
+            nodeList->setMaxConnectionRate(connectionRate);
+        }
+    }
+
+    {   // Fraction of downstream bandwidth reserved for 'hero' avatars:
+        static const QString PRIORITY_FRACTION_KEY = "priority_fraction";
+        if (avatarMixerGroupObject.contains(PRIORITY_FRACTION_KEY)) {
+            bool isDouble = avatarMixerGroupObject[PRIORITY_FRACTION_KEY].isDouble();
+            float priorityFraction = float(avatarMixerGroupObject[PRIORITY_FRACTION_KEY].toDouble());
+            _slavePool.setPriorityReservedFraction(std::min(std::max(0.0f, priorityFraction), 1.0f));
+            qCDebug(avatars) << "Avatar mixer reserving" << priorityFraction << "of bandwidth for priority avatars";
+        }
     }
 
     const QString AVATARS_SETTINGS_KEY = "avatars";
 
     static const QString MIN_HEIGHT_OPTION = "min_avatar_height";
-    float settingMinHeight = domainSettings[AVATARS_SETTINGS_KEY].toObject()[MIN_HEIGHT_OPTION].toDouble(MIN_AVATAR_HEIGHT);
+    float settingMinHeight = avatarMixerGroupObject[MIN_HEIGHT_OPTION].toDouble(MIN_AVATAR_HEIGHT);
     _domainMinimumHeight = glm::clamp(settingMinHeight, MIN_AVATAR_HEIGHT, MAX_AVATAR_HEIGHT);
 
     static const QString MAX_HEIGHT_OPTION = "max_avatar_height";
-    float settingMaxHeight = domainSettings[AVATARS_SETTINGS_KEY].toObject()[MAX_HEIGHT_OPTION].toDouble(MAX_AVATAR_HEIGHT);
+    float settingMaxHeight = avatarMixerGroupObject[MAX_HEIGHT_OPTION].toDouble(MAX_AVATAR_HEIGHT);
     _domainMaximumHeight = glm::clamp(settingMaxHeight, MIN_AVATAR_HEIGHT, MAX_AVATAR_HEIGHT);
 
     // make sure that the domain owner didn't flip min and max
@@ -997,11 +1025,11 @@ void AvatarMixer::parseDomainServerSettings(const QJsonObject& domainSettings) {
                      << "and a maximum avatar height of" << _domainMaximumHeight;
 
     static const QString AVATAR_WHITELIST_OPTION = "avatar_whitelist";
-    _slaveSharedData.skeletonURLWhitelist = domainSettings[AVATARS_SETTINGS_KEY].toObject()[AVATAR_WHITELIST_OPTION]
+    _slaveSharedData.skeletonURLWhitelist = avatarMixerGroupObject[AVATAR_WHITELIST_OPTION]
         .toString().split(',', QString::KeepEmptyParts);
 
     static const QString REPLACEMENT_AVATAR_OPTION = "replacement_avatar";
-    _slaveSharedData.skeletonReplacementURL = domainSettings[AVATARS_SETTINGS_KEY].toObject()[REPLACEMENT_AVATAR_OPTION]
+    _slaveSharedData.skeletonReplacementURL = avatarMixerGroupObject[REPLACEMENT_AVATAR_OPTION]
         .toString();
 
     if (_slaveSharedData.skeletonURLWhitelist.count() == 1 && _slaveSharedData.skeletonURLWhitelist[0].isEmpty()) {
@@ -1018,9 +1046,12 @@ void AvatarMixer::parseDomainServerSettings(const QJsonObject& domainSettings) {
 
 void AvatarMixer::setupEntityQuery() {
     _entityViewer.init();
+    EntityTreePointer entityTree = _entityViewer.getTree();
     DependencyManager::registerInheritance<SpatialParentFinder, AssignmentParentFinder>();
-    DependencyManager::set<AssignmentParentFinder>(_entityViewer.getTree());
-    _slaveSharedData.entityTree = _entityViewer.getTree();
+    DependencyManager::set<AssignmentParentFinder>(entityTree);
+
+    connect(entityTree.get(), &EntityTree::addingEntityPointer, this, &AvatarMixer::entityAdded);
+    connect(entityTree.get(), &EntityTree::deletingEntityPointer, this, &AvatarMixer::entityChange);
 
     // ES query: {"avatarPriority": true, "type": "Zone"}
     QJsonObject priorityZoneQuery;
@@ -1028,6 +1059,7 @@ void AvatarMixer::setupEntityQuery() {
     priorityZoneQuery["type"] = "Zone";
 
     _entityViewer.getOctreeQuery().setJSONParameters(priorityZoneQuery);
+    _slaveSharedData.entityTree = entityTree;
 }
 
 void AvatarMixer::handleOctreePacket(QSharedPointer<ReceivedMessage> message, SharedNodePointer senderNode) {
@@ -1064,6 +1096,25 @@ void AvatarMixer::handleOctreePacket(QSharedPointer<ReceivedMessage> message, Sh
     }
 }
 
+void AvatarMixer::entityAdded(EntityItem* entity) {
+    if (entity->getType() == EntityTypes::Zone) {
+        _dirtyHeroStatus = true;
+        entity->registerChangeHandler([this](const EntityItemID& entityItemID) {
+            this->entityChange();
+        });
+    }
+}
+
+void AvatarMixer::entityRemoved(EntityItem * entity) {
+    if (entity->getType() == EntityTypes::Zone) {
+        _dirtyHeroStatus = true;
+    }
+}
+
+void AvatarMixer::entityChange() {
+    _dirtyHeroStatus = true;
+}
+
 void AvatarMixer::aboutToFinish() {
     DependencyManager::destroy<ResourceManager>();
     DependencyManager::destroy<ResourceCacheSharedItems>();
diff --git a/assignment-client/src/avatars/AvatarMixer.h b/assignment-client/src/avatars/AvatarMixer.h
index 9393ea6c56..f65f04f279 100644
--- a/assignment-client/src/avatars/AvatarMixer.h
+++ b/assignment-client/src/avatars/AvatarMixer.h
@@ -34,8 +34,8 @@ public:
 
     static bool shouldReplicateTo(const Node& from, const Node& to) {
         return to.getType() == NodeType::DownstreamAvatarMixer &&
-               to.getPublicSocket() != from.getPublicSocket() &&
-               to.getLocalSocket() != from.getLocalSocket();
+            to.getPublicSocket() != from.getPublicSocket() &&
+            to.getLocalSocket() != from.getLocalSocket();
     }
 
 public slots:
@@ -80,6 +80,7 @@ private:
 
     // Attach to entity tree for avatar-priority zone info.
     EntityTreeHeadlessViewer _entityViewer;
+    bool _dirtyHeroStatus { true };  // Dirty the needs-hero-update
 
     // FIXME - new throttling - use these values somehow
     float _trailingMixRatio { 0.0f };
@@ -146,6 +147,12 @@ private:
 
     AvatarMixerSlavePool _slavePool;
     SlaveSharedData _slaveSharedData;
+
+public slots:
+    // Avatar zone possibly changed
+    void entityAdded(EntityItem* entity);
+    void entityRemoved(EntityItem* entity);
+    void entityChange();
 };
 
 #endif // hifi_AvatarMixer_h
diff --git a/assignment-client/src/avatars/AvatarMixerClientData.cpp b/assignment-client/src/avatars/AvatarMixerClientData.cpp
index 557c5c9fe3..a6b675efa4 100644
--- a/assignment-client/src/avatars/AvatarMixerClientData.cpp
+++ b/assignment-client/src/avatars/AvatarMixerClientData.cpp
@@ -141,22 +141,15 @@ int AvatarMixerClientData::parseData(ReceivedMessage& message, const SlaveShared
     _avatar->setHasPriorityWithoutTimestampReset(oldHasPriority);
 
     auto newPosition = getPosition();
-    if (newPosition != oldPosition) {
-//#define AVATAR_HERO_TEST_HACK
-#ifdef AVATAR_HERO_TEST_HACK
-        {
-            const static QString heroKey { "HERO" };
-            _avatar->setPriorityAvatar(_avatar->getDisplayName().contains(heroKey));
-        }
-#else
+    if (newPosition != oldPosition || _avatar->getNeedsHeroCheck()) {
         EntityTree& entityTree = *slaveSharedData.entityTree;
         FindPriorityZone findPriorityZone { newPosition, false } ;
         entityTree.recurseTreeWithOperation(&FindPriorityZone::operation, &findPriorityZone);
         _avatar->setHasPriority(findPriorityZone.isInPriorityZone);
-        //if (findPriorityZone.isInPriorityZone) {
-        //    qCWarning(avatars) << "Avatar" << _avatar->getSessionDisplayName() << "in hero zone";
-        //}
-#endif
+        _avatar->setNeedsHeroCheck(false);
+        if (findPriorityZone.isInPriorityZone) {
+            qCWarning(avatars) << "Avatar" << _avatar->getSessionDisplayName() << "in hero zone";
+        }
     }
 
     return true;
diff --git a/assignment-client/src/avatars/AvatarMixerSlave.cpp b/assignment-client/src/avatars/AvatarMixerSlave.cpp
index e59c81f4b7..e7de764708 100644
--- a/assignment-client/src/avatars/AvatarMixerSlave.cpp
+++ b/assignment-client/src/avatars/AvatarMixerSlave.cpp
@@ -43,12 +43,14 @@ void AvatarMixerSlave::configure(ConstIter begin, ConstIter end) {
 
 void AvatarMixerSlave::configureBroadcast(ConstIter begin, ConstIter end, 
                                 p_high_resolution_clock::time_point lastFrameTimestamp,
-                                float maxKbpsPerNode, float throttlingRatio) {
+                                float maxKbpsPerNode, float throttlingRatio,
+                                float priorityReservedFraction) {
     _begin = begin;
     _end = end;
     _lastFrameTimestamp = lastFrameTimestamp;
     _maxKbpsPerNode = maxKbpsPerNode;
     _throttlingRatio = throttlingRatio;
+    _avatarHeroFraction = priorityReservedFraction;
 }
 
 void AvatarMixerSlave::harvestStats(AvatarMixerSlaveStats& stats) {
@@ -308,7 +310,6 @@ namespace {
 }  // Close anonymous namespace.
 
 void AvatarMixerSlave::broadcastAvatarDataToAgent(const SharedNodePointer& node) {
-    const float AVATAR_HERO_FRACTION { 0.4f };
     const Node* destinationNode = node.data();
 
     auto nodeList = DependencyManager::get<NodeList>();
@@ -343,7 +344,7 @@ void AvatarMixerSlave::broadcastAvatarDataToAgent(const SharedNodePointer& node)
 
     // max number of avatarBytes per frame (13 900, typical)
     const int maxAvatarBytesPerFrame = int(_maxKbpsPerNode * BYTES_PER_KILOBIT / AVATAR_MIXER_BROADCAST_FRAMES_PER_SECOND);
-    const int maxHeroBytesPerFrame = int(maxAvatarBytesPerFrame * AVATAR_HERO_FRACTION);  // 5555, typical
+    const int maxHeroBytesPerFrame = int(maxAvatarBytesPerFrame * _avatarHeroFraction);  // 5555, typical
 
     // keep track of the number of other avatars held back in this frame
     int numAvatarsHeldBack = 0;
diff --git a/assignment-client/src/avatars/AvatarMixerSlave.h b/assignment-client/src/avatars/AvatarMixerSlave.h
index 8c5ad6b181..f14e50e11f 100644
--- a/assignment-client/src/avatars/AvatarMixerSlave.h
+++ b/assignment-client/src/avatars/AvatarMixerSlave.h
@@ -110,7 +110,8 @@ public:
     void configure(ConstIter begin, ConstIter end);
     void configureBroadcast(ConstIter begin, ConstIter end, 
                     p_high_resolution_clock::time_point lastFrameTimestamp, 
-                    float maxKbpsPerNode, float throttlingRatio);
+                    float maxKbpsPerNode, float throttlingRatio,
+                    float priorityReservedFraction);
 
     void processIncomingPackets(const SharedNodePointer& node);
     void broadcastAvatarData(const SharedNodePointer& node);
@@ -140,6 +141,7 @@ private:
     p_high_resolution_clock::time_point _lastFrameTimestamp;
     float _maxKbpsPerNode { 0.0f };
     float _throttlingRatio { 0.0f };
+    float _avatarHeroFraction { 0.4f };
 
     AvatarMixerSlaveStats _stats;
     SlaveSharedData* _sharedData;
diff --git a/assignment-client/src/avatars/AvatarMixerSlavePool.cpp b/assignment-client/src/avatars/AvatarMixerSlavePool.cpp
index 013d914cbe..357b347a94 100644
--- a/assignment-client/src/avatars/AvatarMixerSlavePool.cpp
+++ b/assignment-client/src/avatars/AvatarMixerSlavePool.cpp
@@ -76,7 +76,8 @@ void AvatarMixerSlavePool::broadcastAvatarData(ConstIter begin, ConstIter end,
                                                float maxKbpsPerNode, float throttlingRatio) {
     _function = &AvatarMixerSlave::broadcastAvatarData;
     _configure = [=](AvatarMixerSlave& slave) { 
-        slave.configureBroadcast(begin, end, lastFrameTimestamp, maxKbpsPerNode, throttlingRatio);
+        slave.configureBroadcast(begin, end, lastFrameTimestamp, maxKbpsPerNode, throttlingRatio,
+            _priorityReservedFraction);
    };
     run(begin, end);
 }
diff --git a/assignment-client/src/avatars/AvatarMixerSlavePool.h b/assignment-client/src/avatars/AvatarMixerSlavePool.h
index 71a9ace0d3..b05abde2a3 100644
--- a/assignment-client/src/avatars/AvatarMixerSlavePool.h
+++ b/assignment-client/src/avatars/AvatarMixerSlavePool.h
@@ -73,7 +73,10 @@ public:
     void each(std::function<void(AvatarMixerSlave& slave)> functor);
 
     void setNumThreads(int numThreads);
-    int numThreads() { return _numThreads; }
+    int numThreads() const { return _numThreads; }
+
+    void setPriorityReservedFraction(float fraction) { _priorityReservedFraction = fraction; }
+    float getPriorityReservedFraction() const { return  _priorityReservedFraction; }
 
 private:
     void run(ConstIter begin, ConstIter end);
@@ -91,7 +94,11 @@ private:
     ConditionVariable _poolCondition;
     void (AvatarMixerSlave::*_function)(const SharedNodePointer& node);
     std::function<void(AvatarMixerSlave&)> _configure;
+
+    // Set from Domain Settings:
+    float _priorityReservedFraction { 0.4f };
     int _numThreads { 0 };
+
     int _numStarted { 0 }; // guarded by _mutex
     int _numFinished { 0 }; // guarded by _mutex
     int _numStopped { 0 }; // guarded by _mutex
diff --git a/assignment-client/src/avatars/MixerAvatar.h b/assignment-client/src/avatars/MixerAvatar.h
index 3e80704495..01e5e91b44 100644
--- a/assignment-client/src/avatars/MixerAvatar.h
+++ b/assignment-client/src/avatars/MixerAvatar.h
@@ -19,8 +19,12 @@
 
 class MixerAvatar : public AvatarData {
 public:
+    bool getNeedsHeroCheck() const { return _needsHeroCheck; }
+    void setNeedsHeroCheck(bool needsHeroCheck = true)
+        { _needsHeroCheck = needsHeroCheck; }
 
 private:
+    bool _needsHeroCheck { false };
 };
 
 using MixerAvatarSharedPointer = std::shared_ptr<MixerAvatar>;
diff --git a/domain-server/resources/describe-settings.json b/domain-server/resources/describe-settings.json
index 140c7d6c17..352106dcf7 100644
--- a/domain-server/resources/describe-settings.json
+++ b/domain-server/resources/describe-settings.json
@@ -1310,6 +1310,15 @@
           "placeholder": "50",
           "default": "50",
           "advanced": true
+        },
+        {
+            "name": "priority_fraction",
+            "type": "double",
+            "label": "Hero Bandwidth",
+            "help": "Fraction of downstream bandwidth reserved for avatars in 'Hero' zones",
+            "placeholder": "0.40",
+            "default": "0.40",
+            "advanced": true
         }
       ]
     },