diff --git a/common/control.cpp b/common/control.cpp
--- a/common/control.cpp
+++ b/common/control.cpp
@@ -389,8 +389,8 @@
 {
     QList<QVariant>::iterator it;
     QVariantList outputsInfo = getOutputs();
-    const QString sourceHash = source->hashMd5();
-    const QString sourceName = source->name();
+    const QString sourceHash = source ? source->hashMd5() : QStringLiteral("");
+    const QString sourceName = source ? source->name() : QStringLiteral("");
 
     for (it = outputsInfo.begin(); it != outputsInfo.end(); ++it) {
         QVariantMap outputInfo = (*it).toMap();
diff --git a/kcm/config_handler.h b/kcm/config_handler.h
--- a/kcm/config_handler.h
+++ b/kcm/config_handler.h
@@ -47,6 +47,9 @@
     int retention() const;
     void setRetention(int retention);
 
+    KScreen::OutputPtr replicationSource(const KScreen::OutputPtr &output) const;
+    void setReplicationSource(KScreen::OutputPtr &output, const KScreen::OutputPtr &source);
+
     void writeControl();
 
     void checkNeedsSave();
diff --git a/kcm/config_handler.cpp b/kcm/config_handler.cpp
--- a/kcm/config_handler.cpp
+++ b/kcm/config_handler.cpp
@@ -262,6 +262,17 @@
     Q_EMIT changed();
 }
 
+KScreen::OutputPtr ConfigHandler::replicationSource(const KScreen::OutputPtr &output) const
+{
+    return m_control->getReplicationSource(output);
+}
+
+void ConfigHandler::setReplicationSource(KScreen::OutputPtr &output,
+                                         const KScreen::OutputPtr &source)
+{
+    m_control->setReplicationSource(output, source);
+}
+
 void ConfigHandler::writeControl()
 {
     if (!m_control) {
diff --git a/kcm/output_model.h b/kcm/output_model.h
--- a/kcm/output_model.h
+++ b/kcm/output_model.h
@@ -124,7 +124,8 @@
 
     QStringList replicationSourceModel(const KScreen::OutputPtr &output) const;
     bool setReplicationSourceIndex(int outputIndex, int sourceIndex);
-    int replicationSourceIndex(int outputIndex, int sourceId) const;
+    int replicationSourceIndex(int outputIndex) const;
+    int replicationSourceId(const Output &output) const;
 
     QVariantList replicasModel(const KScreen::OutputPtr &output) const;
 
diff --git a/kcm/output_model.cpp b/kcm/output_model.cpp
--- a/kcm/output_model.cpp
+++ b/kcm/output_model.cpp
@@ -70,7 +70,7 @@
     case ReplicationSourceModelRole:
         return replicationSourceModel(output);
     case ReplicationSourceIndexRole:
-        return replicationSourceIndex(index.row(), output->replicationSource());
+        return replicationSourceIndex(index.row());
     case ReplicasModelRole:
         return replicasModel(output);
     case RefreshRatesRole:
@@ -491,17 +491,27 @@
     return hits;
 }
 
+int OutputModel::replicationSourceId(const Output &output) const
+{
+    const KScreen::OutputPtr source = m_config->replicationSource(output.ptr);
+    if (!source) {
+        return 0;
+    }
+    return source->id();
+}
+
 QStringList OutputModel::replicationSourceModel(const KScreen::OutputPtr &output) const
 {
     QStringList ret = { i18n("None") };
 
     for (const auto &out : m_outputs) {
         if (out.ptr->id() != output->id()) {
-            if (out.ptr->replicationSource() == output->id()) {
+            const int outSourceId = replicationSourceId(out);
+            if (outSourceId == output->id()) {
                 // 'output' is already source for replication, can't be replica itself
                 return { i18n("Replicated by other output") };
             }
-            if (out.ptr->replicationSource()) {
+            if (outSourceId) {
                 // This 'out' is a replica. Can't be a replication source.
                 continue;
             }
@@ -521,24 +531,26 @@
     }
 
     Output &output = m_outputs[outputIndex];
-    const int oldSourceId = output.ptr->replicationSource();
+    const int oldSourceId = replicationSourceId(output);
 
     if (sourceIndex < 0) {
         if (oldSourceId == 0) {
             // no change
             return false;
         }
-        output.ptr->setReplicationSource(0);
+        m_config->setReplicationSource(output.ptr, nullptr);
+        output.ptr->setLogicalSize(QSizeF());
         resetPosition(output);
     } else {
-        const int sourceId = m_outputs[sourceIndex].ptr->id();
-        if (oldSourceId == sourceId) {
+        const auto source = m_outputs[sourceIndex].ptr;
+        if (oldSourceId == source->id()) {
             // no change
             return false;
         }
-        output.ptr->setReplicationSource(sourceId);
+        m_config->setReplicationSource(output.ptr, source);
         output.posReset = output.ptr->pos();
-        output.ptr->setPos(m_outputs[sourceIndex].ptr->pos());
+        output.ptr->setPos(source->pos());
+        output.ptr->setLogicalSize(source->logicalSize());
     }
 
     reposition();
@@ -563,8 +575,12 @@
     return true;
 }
 
-int OutputModel::replicationSourceIndex(int outputIndex, int sourceId) const
+int OutputModel::replicationSourceIndex(int outputIndex) const
 {
+    const int sourceId = replicationSourceId(m_outputs[outputIndex]);
+    if (!sourceId) {
+        return 0;
+    }
     for (int i = 0; i < m_outputs.size(); i++) {
         const Output &output = m_outputs[i];
         if (output.ptr->id() == sourceId) {
@@ -580,7 +596,7 @@
     for (int i = 0; i < m_outputs.size(); i++) {
         const Output &out = m_outputs[i];
         if (out.ptr->id() != output->id()) {
-            if (out.ptr->replicationSource() == output->id()) {
+            if (replicationSourceId(out) == output->id()) {
                 ret << i;
             }
         }
diff --git a/kded/config.cpp b/kded/config.cpp
--- a/kded/config.cpp
+++ b/kded/config.cpp
@@ -207,11 +207,6 @@
             if (!out) {
                 return;
             }
-            QString replicationSourceHash;
-            if (int sourceId = out->replicationSource()) {
-                replicationSourceHash = m_data->output(sourceId)->hashMd5();
-            }
-            info[QStringLiteral("replicate")] = replicationSourceHash;
 
             QVariantMap pos;
             pos[QStringLiteral("x")] = out->pos().x();
diff --git a/kded/output.cpp b/kded/output.cpp
--- a/kded/output.cpp
+++ b/kded/output.cpp
@@ -327,18 +327,6 @@
             }
             infoFound = true;
             readIn(output, info, control.getOutputRetention(output));
-
-            const QString replicationSourceHash = info[QStringLiteral("replicate")].toString();
-            if (replicationSourceHash.isEmpty()) {
-                output->setReplicationSource(0);
-            } else {
-                for (const KScreen::OutputPtr out : outputs) {
-                    if (out != output && out->hashMd5() == replicationSourceHash) {
-                        output->setReplicationSource(out->id());
-                        break;
-                    }
-                }
-            }
             break;
         }
         if (!infoFound) {
@@ -352,8 +340,22 @@
             }
         }
     }
+
+    for (KScreen::OutputPtr output : outputs) {
+        auto replicationSource = control.getReplicationSource(output);
+        if (replicationSource) {
+            output->setPos(replicationSource->pos());
+            output->setLogicalSize(replicationSource->logicalSize());
+        } else {
+            output->setLogicalSize(QSizeF());
+        }
+    }
+
+    // TODO: this does not work at the moment with logical size replication. Deactivate for now.
     // correct positional config regressions on global output data changes
+#if 0
     adjustPositions(config, outputsInfo);
+#endif
 }
 
 static QVariantMap metadata(const KScreen::OutputPtr &output)