diff --git a/LuaLibs/ProcessLapJoint.lua b/LuaLibs/ProcessLapJoint.lua
index 1931197..5526401 100644
--- a/LuaLibs/ProcessLapJoint.lua
+++ b/LuaLibs/ProcessLapJoint.lua
@@ -6966,8 +6966,10 @@ local function MakeLongMoreFaces( Proc, nPhase, nRawId, nPartId, dOvmHead)
       -- superficie di fondo
       nSurfBottomId = EgtSurfTmPlaneInBBox( nAddGrpId, ptMaxBox, vtOrtho, b3SolidExtended, GDB_ID.ROOT)
       -- calcolo di quanto allargare le superfici
-      local dWidth = EgtIf( Proc.AffectedFaces.Front, Proc.Box:getDimZ(), Proc.Box:getDimY())
-      dAddLen = min( dWidth, 100) / 2
+      if not dAddLen then
+         local dWidth = EgtIf( Proc.AffectedFaces.Front, Proc.Box:getDimZ(), Proc.Box:getDimY())
+         dAddLen = min( dWidth, 100) / 2
+      end
    end
    -- la divido in parti lungo X
    local vAddId = {}