diff --git a/Detectors/Upgrades/ALICE3/TRK/simulation/src/Detector.cxx b/Detectors/Upgrades/ALICE3/TRK/simulation/src/Detector.cxx
index e0fc6ef1ed35b..06fd2d9670b67 100644
--- a/Detectors/Upgrades/ALICE3/TRK/simulation/src/Detector.cxx
+++ b/Detectors/Upgrades/ALICE3/TRK/simulation/src/Detector.cxx
@@ -128,7 +128,7 @@ void Detector::buildTRKMiddleOuterLayers()
       LOGP(info, "TRKLayer created. Name: {}", GeometryTGeo::getTRKLayerPattern() + std::to_string(0));
       mLayers.emplace_back(1, GeometryTGeo::getTRKLayerPattern() + std::to_string(1), 11.f, 10, 100.e-3);
       mLayers.emplace_back(2, GeometryTGeo::getTRKLayerPattern() + std::to_string(2), 15.f, 10, 100.e-3);
-      mLayers.emplace_back(3, GeometryTGeo::getTRKLayerPattern() + std::to_string(3), 19.f, 10, 100.e-3);
+      mLayers.emplace_back(3, GeometryTGeo::getTRKLayerPattern() + std::to_string(3), 20.f, 10, 100.e-3);
       mLayers.emplace_back(4, GeometryTGeo::getTRKLayerPattern() + std::to_string(4), 30.f, 10, 100.e-3);
       mLayers.emplace_back(5, GeometryTGeo::getTRKLayerPattern() + std::to_string(5), 45.f, 20, 100.e-3);
       mLayers.emplace_back(6, GeometryTGeo::getTRKLayerPattern() + std::to_string(6), 60.f, 20, 100.e-3);
diff --git a/Detectors/Upgrades/ALICE3/TRK/simulation/src/TRKLayer.cxx b/Detectors/Upgrades/ALICE3/TRK/simulation/src/TRKLayer.cxx
index c4683f28918d0..8d30cf9759e40 100644
--- a/Detectors/Upgrades/ALICE3/TRK/simulation/src/TRKLayer.cxx
+++ b/Detectors/Upgrades/ALICE3/TRK/simulation/src/TRKLayer.cxx
@@ -168,7 +168,7 @@ TGeoVolume* TRKLayer::createChip(std::string type)
 
 TGeoVolume* TRKLayer::createModule(std::string type)
 {
-  TGeoMedium* medAir = gGeoManager->GetMedium("TRK_AIR$");
+  TGeoMedium* medSi = gGeoManager->GetMedium("TRK_SILICON$");
   std::string moduleName = GeometryTGeo::getTRKModulePattern() + std::to_string(mLayerNumber);
 
   TGeoShape* module;
@@ -176,7 +176,7 @@ TGeoVolume* TRKLayer::createModule(std::string type)
 
   if (type == "cylinder") {
     module = new TGeoTube(mInnerRadius, mInnerRadius + mChipThickness, (constants::moduleMLOT::length * mNumberOfModules) / 2);
-    moduleVol = new TGeoVolume(moduleName.c_str(), module, medAir);
+    moduleVol = new TGeoVolume(moduleName.c_str(), module, medSi);
 
     TGeoVolume* chipVol = createChip("cylinder");
     LOGP(debug, "Inserting {} in {} ", chipVol->GetName(), moduleVol->GetName());
@@ -186,7 +186,7 @@ TGeoVolume* TRKLayer::createModule(std::string type)
     double moduleLength = constants::moduleMLOT::length;
 
     module = new TGeoBBox(moduleWidth / 2, mChipThickness / 2, moduleLength / 2); // TO BE CHECKED !!!
-    moduleVol = new TGeoVolume(moduleName.c_str(), module, medAir);
+    moduleVol = new TGeoVolume(moduleName.c_str(), module, medSi);
 
     for (int iChip = 0; iChip < mHalfNumberOfChips; iChip++) {
       TGeoVolume* chipVolLeft = createChip("flat");
@@ -223,7 +223,7 @@ TGeoVolume* TRKLayer::createModule(std::string type)
 
 TGeoVolume* TRKLayer::createHalfStave(std::string type)
 {
-  TGeoMedium* medAir = gGeoManager->GetMedium("TRK_AIR$");
+  TGeoMedium* medSi = gGeoManager->GetMedium("TRK_SILICON$");
   std::string halfStaveName = GeometryTGeo::getTRKHalfStavePattern() + std::to_string(mLayerNumber);
 
   TGeoShape* halfStave;
@@ -231,7 +231,7 @@ TGeoVolume* TRKLayer::createHalfStave(std::string type)
 
   if (type == "cylinder") {
     halfStave = new TGeoTube(mInnerRadius, mInnerRadius + mChipThickness, mChipLength / 2);
-    halfStaveVol = new TGeoVolume(halfStaveName.c_str(), halfStave, medAir);
+    halfStaveVol = new TGeoVolume(halfStaveName.c_str(), halfStave, medSi);
 
     TGeoVolume* moduleVol = createModule("cylinder");
     LOGP(debug, "Inserting {} in {} ", moduleVol->GetName(), halfStaveVol->GetName());
@@ -242,7 +242,7 @@ TGeoVolume* TRKLayer::createHalfStave(std::string type)
     double halfStaveLength = constants::moduleMLOT::length * mNumberOfModules;
 
     halfStave = new TGeoBBox(halfStaveWidth / 2, mChipThickness / 2, halfStaveLength / 2);
-    halfStaveVol = new TGeoVolume(halfStaveName.c_str(), halfStave, medAir);
+    halfStaveVol = new TGeoVolume(halfStaveName.c_str(), halfStave, medSi);
 
     for (int iModule = 0; iModule < mNumberOfModules; iModule++) {
       TGeoVolume* moduleVol = createModule("flat");
@@ -257,6 +257,9 @@ TGeoVolume* TRKLayer::createHalfStave(std::string type)
       halfStaveVol->AddNode(moduleVol, iModule, trans);
     }
   }
+
+  halfStaveVol->SetLineColor(kYellow);
+
   return halfStaveVol;
 }
 
@@ -296,11 +299,11 @@ TGeoVolume* TRKLayer::createStave(std::string type)
       staveVol->AddNode(moduleVol, iModule, trans);
     }
   } else if (type == "staggered") {
-    /*double moduleWidth = constants::moduleMLOT::width;
-    double moduleLength = constants::moduleMLOT::length;*/
+    double overlap = constants::moduleMLOT::gaps::outerEdgeLongSide + constants::moduleMLOT::chip::passiveEdgeReadOut + 0.1; // 1.5mm outer-edge + 1mm deadzone + 1mm (true)overlap
+    double shift = overlap / 2;
 
-    double halfstaveWidth = constants::ML::width;
-    double staveWidth = constants::OT::width; // Each stave has two modules (based on the LOI design)
+    double halfstaveWidth = constants::OT::halfstave::width;
+    double staveWidth = constants::OT::width - overlap;
     double staveLength = constants::moduleMLOT::length * mNumberOfModules;
 
     stave = new TGeoBBox(staveWidth / 2, mLogicalVolumeThickness / 2, staveLength / 2);
@@ -311,12 +314,12 @@ TGeoVolume* TRKLayer::createStave(std::string type)
     TGeoVolume* halfStaveVolRight = createHalfStave("flat");
 
     TGeoCombiTrans* transLeft = new TGeoCombiTrans();
-    transLeft->SetTranslation(-halfstaveWidth / 2 + 0.05, 0, 0); // TO BE CHECKED !!! 1mm overlap between the modules
+    transLeft->SetTranslation(-halfstaveWidth / 2 + shift, 0, 0); // TO BE CHECKED !!! 1mm overlap between the modules
     LOGP(debug, "Inserting {} in {} ", halfStaveVolLeft->GetName(), staveVol->GetName());
     staveVol->AddNode(halfStaveVolLeft, 0, transLeft);
 
     TGeoCombiTrans* transRight = new TGeoCombiTrans();
-    transRight->SetTranslation(halfstaveWidth / 2 - 0.05, 0.2, 0); // TO BE CHECKED !!! 1mm overlap between the modules
+    transRight->SetTranslation(halfstaveWidth / 2 - shift, 0.2, 0); // TO BE CHECKED !!! 1mm overlap between the modules
     LOGP(debug, "Inserting {} in {} ", halfStaveVolRight->GetName(), staveVol->GetName());
     staveVol->AddNode(halfStaveVolRight, 1, transRight);
   } else {
@@ -377,7 +380,7 @@ void TRKLayer::createLayer(TGeoVolume* motherVolume)
       // Put the staves in the correct position and orientation
       TGeoCombiTrans* trans = new TGeoCombiTrans();
       double theta = 360. * iStave / nStaves;
-      TGeoRotation* rot = new TGeoRotation("rot", theta + 90 + 3, 0, 0);
+      TGeoRotation* rot = new TGeoRotation("rot", theta - 90 + 3, 0, 0);
       trans->SetRotation(rot);
       trans->SetTranslation(mInnerRadius * std::cos(2. * TMath::Pi() * iStave / nStaves), mInnerRadius * std::sin(2 * TMath::Pi() * iStave / nStaves), 0);
 
@@ -385,13 +388,15 @@ void TRKLayer::createLayer(TGeoVolume* motherVolume)
       layerVol->AddNode(staveVol, iStave, trans);
     }
   } else if (mLayout == kStaggered) {
+    double overlapInStave = constants::moduleMLOT::gaps::outerEdgeLongSide + constants::moduleMLOT::chip::passiveEdgeReadOut + 0.1; // 1.5mm outer-edge + 1mm deadzone + 1mm (true)overlap
+
     double layerLength = constants::moduleMLOT::length * mNumberOfModules;
+    double staveWidth = constants::OT::width - overlapInStave;
 
     layer = new TGeoTube(mInnerRadius - 0.333 * layerThickness, mInnerRadius + 0.667 * layerThickness, layerLength / 2);
     layerVol = new TGeoVolume(mLayerName.c_str(), layer, medAir);
 
     // Compute the number of staves
-    double staveWidth = constants::OT::width; // Each stave has two modules (based on the LOI design)
     int nStaves = (int)std::ceil(mInnerRadius * 2 * TMath::Pi() / staveWidth);
     nStaves += nStaves % 2; // Require an even number of staves
 
@@ -410,7 +415,7 @@ void TRKLayer::createLayer(TGeoVolume* motherVolume)
       // Put the staves in the correct position and orientation
       TGeoCombiTrans* trans = new TGeoCombiTrans();
       double theta = 360. * iStave / nStaves;
-      TGeoRotation* rot = new TGeoRotation("rot", theta + 90, 0, 0);
+      TGeoRotation* rot = new TGeoRotation("rot", theta - 90 + 3, 0, 0);
       trans->SetRotation(rot);
       trans->SetTranslation(mInnerRadius * std::cos(2. * TMath::Pi() * iStave / nStaves), mInnerRadius * std::sin(2 * TMath::Pi() * iStave / nStaves), 0);