[Joey Milia]

Could you provide a pic of the internals, it's hard to say much just seeing the plates.

Consider how you are mounting the gearbox. Having that angle on the bottom won't help and I don't see any mounting holes already.

It doesn't seem to be a shifting transmission in which case it can be a lot thiner.

You should also reconsider your uses of a 17 tooth gear, I don't know where you plan to get it but something like 16 teeth is much more common.

Tristan has a good point, what benefit does this have over an andymark product? If your goal is to make something smaller/lighter than you could start with toughbox gearing and go from there.