I like the profile on the teeth, its a shame you had to thin them down. So the top & bottom armour rings are just screwed into the 8mm aluminium plates now? Given how easily I had 10mm ali bent in featherweights, its not going to last long. 3D printed internal parts can work well if they are thick and printed with 100% in-fill, but its risky to use them for anything structural. If possible, prototype parts with 3D printing and then mill them from HDPE, nylon or acetal for extra strength.