First version with bayonet mount

constants.scad

@@ -13,6 +13,7 @@ groove_length = 50;
 
 // Top
 bumper_height = 15;
-bumper_edge_radius = 5;
-bumper_diameter = 80;
+bumper_diameter = 85;
+// Flat surface starts after bumper_edge_radius from the outside
+bumper_edge_radius = bumper_diameter - tube_outer_diameter - 4;
 bumper_tube_depth = 4;

lid.scad

@@ -1,11 +1,14 @@
 include <constants.scad>;
 include <bayonetmount.scad>;
 
+delta = 0.2;
+wall_thickness = 5;
+
 difference() {
-	lid(tube_outer_diameter, 
-		tube_inner_diameter,
-		latch_width,
-		latch_height,
+	lid(tube_outer_diameter - delta * 2, 
+		tube_inner_diameter - delta * 2,
+		latch_width - delta,
+		latch_height - delta,
 		lid_height);
 	
 	hull() {
@@ -14,4 +17,17 @@ difference() {
 				translate([x, 0, lid_height])
 					sphere(r = groove_depth, center = true);
 	}
+	
+	difference() {
+		translate([0, 0, (lid_height - wall_thickness) / 2])
+			cylinder(r = (tube_inner_diameter - wall_thickness) / 2, 
+						h = lid_height - wall_thickness,
+						center = true);
+		
+		translate([0, 0, lid_height / 2])
+			cube([tube_outer_diameter, 
+					groove_depth * 2, 
+					lid_height],
+					center = true);
+	}
 }

top.scad

@@ -2,6 +2,21 @@ include <constants.scad>;
 include <bayonetmount.scad>;
 
 
+module support(outer_diameter, height) {
+	inner_diameter = outer_diameter - 0.5;
+	
+	difference() {
+		cylinder(r = outer_diameter / 2, 
+					h = height,
+					center=true);
+		cylinder(r = inner_diameter / 2, 
+					h = height * 1.01, 
+					center = true);
+	}
+}
+
+
+
 difference() {
 	translate([0, 0, bumper_height / 2])
 		minkowski() {
@@ -28,4 +43,11 @@ difference() {
 		cylinder(r = tube_outer_diameter / 2,
 					h = bumper_tube_depth, 
 					center = true);
-}
+}
+
+
+translate([0, 0, bumper_tube_depth / 2])
+	support(tube_inner_diameter + 0.5, bumper_tube_depth);
+
+translate([0, 0, bumper_height - lid_height + latch_height / 2])
+	support(tube_inner_diameter + 0.5, latch_height);