The gearbox looks fine. Are you planning on building it in the 2 weeks of off-season we have left?
Is this intended for a WCD? If so, that output shaft would be far too short. I'm not sure if Vex sells a ballshifter with a longer shaft though.
It looks like you can save quite a bit of weight and material if you move the 4 corner standoffs closer to the center and "round out" the corners. You can even just ditch the 4 corner standoffs and use the screws for the CIMs to hold the gearbox together, like the
WCP DS does.
The only problem I have with this gearbox is that the CIMs aren't black
.
The picture looks like a screenshot anyways; do you know how to render CAD? (I'm asking because you said this is your first gearbox). If you don't, say what software you use and I'm sure someone can help you.