diff --git a/common-tools/clas-jcsg/src/main/java/org/jlab/detector/geant4/v2/DCGeant4Factory.java b/common-tools/clas-jcsg/src/main/java/org/jlab/detector/geant4/v2/DCGeant4Factory.java
index 574999888..28e5782fa 100644
--- a/common-tools/clas-jcsg/src/main/java/org/jlab/detector/geant4/v2/DCGeant4Factory.java
+++ b/common-tools/clas-jcsg/src/main/java/org/jlab/detector/geant4/v2/DCGeant4Factory.java
@@ -581,7 +581,7 @@ public final class DCGeant4Factory extends Geant4Factory {
     private int nsgwires;
 
     private final double y_enlargement = 3.65;
-    private final double z_enlargement = -2.96;
+    private final double z_enlargement = -2.46;
     private final double microgap = 0.01;
 
     private final Wire[][][][] wires;
@@ -889,20 +889,30 @@ public Geant4Basic createRegion(int isector, int iregion) {
         return regionVolume;
     }
 
-    ///////////////////////////////////////////////////
+
+    /**
+     * Create GEANT4 superlayer volume:
+     * - from first to last guard wire in layer=0 to define y 
+     * - from first to last guard wire plane in z 
+     * @param isuper
+     * @return
+     */
     public Geant4Basic createSuperlayer(int isuper) {
         int nsglayers = dbref.nsenselayers(isuper) + dbref.nguardlayers(isuper);
-        Wire lw0 = new Wire(1, isuper, 1, 0);
-        Wire lw1 = new Wire(1, isuper, nsglayers-2, nsgwires - 1);
+        Wire lw0 = new Wire(1, isuper, 0, 0);
+        Wire lw1 = new Wire(1, isuper, 0, nsgwires - 1);
+        Wire lw2 = new Wire(1, isuper, 2, 0);
 
-        Vector3d midline = lw1.mid().minus(lw0.mid());
-        double lay_dy = Math.sqrt(Math.pow(midline.magnitude(), 2.0) - Math.pow(midline.dot(lw0.dir()), 2.0)) / 2.0;
+        Vector3d yline = lw1.mid().minus(lw0.mid());
+        double lay_dy = Math.sqrt(Math.pow(yline.magnitude(), 2.0) - Math.pow(yline.dot(lw0.dir()), 2.0)) / 2.0;
         double lay_dx0 = lw0.length() / 2.0;
         double lay_dx1 = lw1.length() / 2.0;
-        double lay_dz = (dbref.cellthickness(isuper)*dbref.nsenselayers(isuper)+1) * dbref.wpdist(isuper) / 2.0;
+        double lay_dz = (dbref.cellthickness(isuper)*dbref.nsenselayers(isuper)+1) * dbref.wpdist(isuper)/Math.cos(dbref.thtilt(isuper/2))/ 2.0;
         double lay_skew = lw0.center().minus(lw1.center()).angle(lw1.dir()) - Math.toRadians(90.0);
 
-        Vector3d lcent = lw0.center().plus(lw1.center()).dividedBy(2.0);
+        Vector3d zline = lw2.mid().minus(lw0.mid()).normalized();
+        Vector3d lcent = lw0.center().plus(lw1.center()).dividedBy(2.0).plus(zline.times(lay_dz));
+        
         G4Trap superlayerVolume = new G4Trap("sl" + (isuper + 1),
                 lay_dz, -dbref.thtilt(isuper / 2), Math.toRadians(90.0),
                 lay_dy, lay_dx0, lay_dx1, lay_skew,