diff --git a/Surf-Fins-10inch.json b/Surf-Fins-10inch.json
index f79dc7e..10346a0 100644
--- a/Surf-Fins-10inch.json
+++ b/Surf-Fins-10inch.json
@@ -98,7 +98,7 @@
         },
         "New set 3": {
             "$fn": "64",
-            "base_extra_thickness": "40",
+            "base_extra_thickness": "20",
             "base_tickness": "8",
             "build_box": "false",
             "build_fin": "false",
diff --git a/Surf-Fins-10inch.scad b/Surf-Fins-10inch.scad
index e997ae9..9737ae9 100644
--- a/Surf-Fins-10inch.scad
+++ b/Surf-Fins-10inch.scad
@@ -12,9 +12,10 @@ include <DotScad/src/ellipse_extrude.scad>;
 include <DotScad/src/loft.scad>;
 
 include <scad-utils/morphology.scad>;
-include <common.scad>
+include <common.scad>;
 
 include <./lib/chinook.scad> // US Box
+include <./lib/finbox_us.scad> // US Box
 
 
 // https://github.com/BelfrySCAD/BOSL2/wiki/Tutorial-Beziers_for_Beginners
@@ -76,7 +77,7 @@ fin_back_strength=30;
 /* [Base Specs] */
 
 base_tickness=8; 
-base_extra_thickness=40;
+base_extra_thickness=20;
 
 
 // ---------------------*/
@@ -96,6 +97,8 @@ resin_escape_diameter   = 4;
 merge_holes_diameter = 6;
 piston_depth = 5;
 
+skirt_angle=80;
+
 // ---------------------*/
 /*        [US Box]        */
 // ---------------------*/
@@ -262,13 +265,10 @@ if (draw_profile) {
     left (800) color ("Green") polygon(profile_curve_with_base);
     
        left (1000) color ("Green") shell(10) polygon(profile_curve_with_base);
-    
 }    
 
 
 
-
-
 // *****************
 // *  Fin Drawing  *
 // *****************
@@ -313,6 +313,28 @@ module buildBoxMold() {
 }
 
 
+
+
+/**
+ * Remove bottom part of the fin mold to let the box mold do the job
+ *
+ */
+module moldBottomMask(moldThickness = 3,height,angle) {
+
+    // Remove bottom part 
+    //color("Red") cube([fin_width,base_extra_thickness,80],anchor=BACK);
+    deviation = opp_ang_to_adj (height,angle);
+    //back(moldThickness)
+    back(-1)
+    down(OFFSET)
+    //up(2)
+    color ("Blue") prismoid(
+                size1=[fin_width/2*1.2, moldThickness*2], 
+                size2=[fin_width/2*1.2, moldThickness*2+ 2*deviation], 
+                h=height+OFFSET*2 
+            );
+}
+
 /**
  * Build mold
  * 
@@ -327,18 +349,47 @@ module buildMold() {
     
     // Bottom Mold
     if (mold_part != "top") {
+    
+        // Fin mold
         difference() {
             union() {
                 down(moldHeight) linear_extrude (moldHeight) polygon(moldContour);  // bottom 
                 //back(5) left(95) cube([20+10,25,moldHeight],anchor=BACK+TOP);          // Box shell
-                skirt( profile, moldThickness = 3 , angle = 85, moldDeep = fin_thickness );
-                //up(5) color("Yellow") left(80) buildBoxMold();
+                difference() {
+                    skirt( profile, moldThickness = 3 , angle = skirt_angle, moldDeep = fin_thickness );
+                    moldBottomMask(height=fin_thickness * 3,angle=skirt_angle);
+                    
+                    
+                    //
+                    //moldJunctionMask(height=fin_thickness * 3,angle=skirt_angle);
+                }
                 
             };
+            // Remove Fin
             buildCompletFin();
         }
+        // Box mold
+        assert (fin_base,"fin_base missing");
+        echo ("fin_base----------",fin_base);
+        //          left(80) finBoxMold( length = 130, finLength = fin_base );
+        //diff() {
+        difference() {
+            left(80) finBoxMold( fin_base+30,skirtAngle = skirt_angle );
+            
+            // Remove junction between skirt
+            //tag("remove")
+            moldJunctionMask(height=fin_thickness * 3,angle=skirt_angle);
+            //tag("remove")        
+            buildCompletFin();       
+        }
+        //moldJunctionMask(height=fin_thickness * 3,angle=skirt_angle);
+        
+        
+        
     }
     
+    up(50) buildCompletFin();
+    
     //left(300) linear_extrude (skirtHeight) polygon(moldSkirtRegion);
     /*
     if (mold_part !=  "top") 
@@ -363,6 +414,24 @@ module buildMold() {
         }      
     */    
 }
+
+module moldJunctionMask(moldThickness = 3,height,angle){
+
+    deviation = opp_ang_to_adj (height,angle);
+    right(moldThickness)
+    left(moldThickness/2)
+    down(OFFSET)
+    //fwd(60)
+    //back(moldThickness*2-0.5)
+    back(moldThickness*1.2-OFFSET )
+        color("Red") 
+            prismoid(
+                size1=[fin_width/2-1.5*moldThickness, moldThickness*3+2*OFFSET], 
+                size2=[fin_width/2+1*deviation+0*moldThickness, /*moldThickness/2*/moldThickness * 3+deviation], 
+                h=height+OFFSET*3 
+            );
+}
+
 module buildMoldSkirt( height,offset,thickness ) {
     outside = expandPath(profile,offset);
     inside = expandPath(profile,offset-thickness);
diff --git a/lib/finbox_us.scad b/lib/finbox_us.scad
index a5a5d65..a3cd061 100644
--- a/lib/finbox_us.scad
+++ b/lib/finbox_us.scad
@@ -60,6 +60,8 @@ module usBox( length, height=23, thickness = 9, tabLength = 20,pinDiameter = 5,p
 
 module usBoxMold( length, height=23, thickness = 9, moldThickness = 4,tabLength = 20,part = "bottom",skirtAngle=80 ) {
 
+//assert(length == 130,"Not 130");
+
     moldHeight = thickness + 2 * moldThickness;
     skirtHeight = 3 * thickness;
     deviation = opp_ang_to_adj (skirtHeight,skirtAngle);    // Skirt devitation
@@ -127,13 +129,12 @@ module usBoxMold( length, height=23, thickness = 9, moldThickness = 4,tabLength
     
 }
 
-module finBoxMold(length,finLength,part="bottom") {
+module finBoxMold( length, finLength=-1, skirtAngle = 80, part="bottom") {
 
+    assert (finLength,"Missing 'finLength' parameter in finBoxMold module");
     //if (part=="bottom") {
-        usBoxMold( 130,finLength=100,part=part );
+    usBoxMold( length,part=part,skirtAngle=skirtAngle );
     //}
-  
-
     
 }
 
@@ -163,7 +164,6 @@ module thickness_cut(thickness,height) {
 //usBox( 130,drill=false );
 //usBoxMold( 130,part="top" );
 
-finBoxMold( 130,finLength=100,part="bottom" );
 
 
 //down(50) usBoxMold( 130,part="bottom" );