diff --git a/LuaLibs/ProcessLapJoint.lua b/LuaLibs/ProcessLapJoint.lua
index 590a715..a3e5867 100644
--- a/LuaLibs/ProcessLapJoint.lua
+++ b/LuaLibs/ProcessLapJoint.lua
@@ -5571,7 +5571,6 @@ local function MakeLongMoreFaces( Proc, nPhase, nRawId, nPartId, dOvmHead)
    if Proc.Topology == 'Tunnel' and Proc.AffectedFaces.Front then
       bAddEndCapLeftSide = true
       bAddEndCapRightSide = true
-      dAddLen = 225
       -- recupero centro e normale delle facce
       local vtN = {}
       for i = 1, Proc.Fct do
@@ -5596,6 +5595,9 @@ local function MakeLongMoreFaces( Proc, nPhase, nRawId, nPartId, dOvmHead)
       b3SolidExtended:expand( 100 * GEO.EPS_SMALL)
       -- superficie di fondo
       nSurfBottomId = EgtSurfTmPlaneInBBox( nAddGrpId, ptMaxBox, vtOrtho, b3SolidExtended, GDB_ID.ROOT)
+      -- calcolo di quanto allargare le superfici
+      local dWidth = b3Raw:getDimY()
+      dAddLen = min( dWidth, 100) / 2
    end
    -- la divido in parti lungo X
    local vAddId = {}