diff --git a/amt-box.scad b/amt-box.scad
index 2e75c0d..8da65e1 100644
--- a/amt-box.scad
+++ b/amt-box.scad
@@ -3,15 +3,17 @@
  * Dynavox AMT-1 and Wavecor WF145WA05
  */
 
-B = 12.7; // Bushing outer diameter
+B1 = 19.05; // Bushing outer diameter
+B2 = 12.7;
 M = 6.35; // Mill diameter
 J = 100; // Mill pad
 T = 21; // Material thickness
 I = 320; // Internal dimension
 A = 5; // Alignment pad size
-P = 17; // Alignment pad placement
+P = 16; // Alignment pad placement
 O = I + 2 * T; // Outer dimensions
-BD = B - M; // Bushing offset
+BD = B1 - M; // Bushing offset
+BD2 = B2 - M;
 
 W = 200 - 40; // Internal width
 H = 350 - 40; // Internal height/depth
@@ -23,57 +25,64 @@ module sam300d_flush_mount() {
 }
 
 // Side panels
-translate([I+J/2, 0]) {
+translate([250, 0]) {
   difference() {
     square([H - BD, H + 100], center=true);
-    translate([-H/2 + 100 , -H/2 + 60]) circle(d=100, $fn=100); // !!!
-    offset(r=BD/2) square([80+M,M], center=true);
+      
+    // Bass reflex tube
+    translate([-H/2 + 100 , -350/2 + 80]) circle(d=69-0.4+BD, $fn=100);
+    translate([H/2 - 100 , -350/2 + 80]) circle(d=69-0.4+BD, $fn=100);
+      
+    // Bracing tenon
+    translate([0, 350/2-200+6]) offset(r=BD/2) square([80+M,M], center=true);
    
       
     // Alignment squares
-    translate([O/2,0]) rotate(45) square(A, center=true);
-    translate([-O/2,0]) rotate(45) square(A, center=true);
-    translate([0,I/2-P]) rotate(45) square(A, center=true);
-    translate([0,-I/2+P]) rotate(45) square(A, center=true);
-    translate([I/2,I/2-P]) rotate(45) square(A, center=true);
-    translate([I/2,-I/2+P]) rotate(45) square(A, center=true);
-    translate([-I/2,I/2-P]) rotate(45) square(A, center=true);
-    translate([-I/2,-I/2+P]) rotate(45) square(A, center=true);
+    translate([H/2-P,0]) rotate(45) square(A, center=true);
+    translate([-H/2+P,0]) rotate(45) square(A, center=true);
+    translate([0,H/2-P]) rotate(45) square(A, center=true);
+    translate([0,-H/2+P]) rotate(45) square(A, center=true);
   }
 }
 
 // Back face + bottom/top cutout
-translate([-I-J/2, 0])
+translate([-170, 0])
 difference() {
   square([W - BD, H + 100], center=true);
-  offset(r=BD/2)  square([93 - BD, 80 - BD], center=true);
+    difference() {
+      offset(r=BD/2) square([93, 80], center=true);
+      offset(r=BD/2) square([76, 56], center=true);
+    }
     translate([0,H/2]) rotate(45) square(A, center=true);
     translate([0,-H/2]) rotate(45) square(A, center=true);
     translate([-W/2+P,0]) rotate(45) square(A, center=true);
     translate([W/2-P,0]) rotate(45) square(A, center=true);
-
 }
 
-// Mounting holes
+// Front mounting holes
 difference() {
-  square([W, H], center=true);
+  square([W-BD2, H-BD2], center=true);
+
+  // Alignment squares
+  translate([0,H/2-P]) rotate(45) square(A, center=true);
+  translate([0,-H/2+P]) rotate(45) square(A, center=true);
+  translate([-W/2+P,0]) rotate(45) square(A, center=true);
+  translate([W/2-P,0]) rotate(45) square(A, center=true);
     
   // Tweeter
-  translate([0, H/2-80]) {
-      circle(d=65 + BD, $fn=100);
+  translate([0, 350/2-80]) {
+      circle(d=65 + BD2, $fn=100);
       translate([-56/2,-56/2]) circle(d=4, $fn=30);
       translate([56/2,-56/2]) circle(d=4, $fn=30);
       translate([-56/2,56/2]) circle(d=4, $fn=30);
       translate([56/2,56/2]) circle(d=4, $fn=30);
-    
   }
   
   // Woofer
-  translate([0, H/2-200]) {
-    circle(d=118 + BD, $fn=100);
+  translate([0, 350/2-200]) {
+    circle(d=118 + BD2, $fn=100);
     for ( i = [45 : 90 : 360] ){
       rotate(i) translate([138/2,0]) circle(d=4, $fn=30);
     }
-    
   }
 }
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