I thought I share with you guy's what I made
I could'nt find any diff covers for my cars, everybody was out of stock. So I decided to make my own using the lexan leftover from cutting out the wheel opennings on the bodies. Withe the 416 half the diff balls are exposed so I needed to do somthing. From the Pics I used clear on the 416, it now serves as an inspection window too. On the 415 I used white. You basically just use the pulley as a template and cut with lexan scissors, next I used the body reamer for the center hole. And bam your DIY diff covers
415

416

and the body I used when I cut the wheel openings

since I built the cars I have never rebuilt the diffs even after 6 races and practicing everyday on some light dust asphalt