pic: VersaDrop GrassHopper Drive

[Cothron Theiss]

First off, thank you for posting the native SolidWorks Files in your GrabCAD. That makes life so much easier.

Looking at your model, the back Colsons are raised up by 1/8". I'm wondering if those wheels are needed at all, considering how little they'll actually be contacting the floor. For the sake of simplicity, it might be good to just drop that back set all together and push the Omni's back to where the Colsons were. Also, I would make a slight change to how your drive rails are connected to your front and back framing rails. Since you have a chain-in-tube aspect, having the fronts and backs of your drive rails open makes life MUCH easier if you have to make any changes or fixes with your chain.
Don't forget that you'll need bumper mounts; per 2016 rules, you couldn't have spans of unsupported bumpers over 8", and right now you've got a span of about 10" where your drop modules are.
Also, +1 to everyone who's mentioned actuating or other methods of transferring the weight of the robot to your middle wheel when strafing. My team built a standard H drive during prototyping for 2015, and it was pretty useless. Part of it was our gear ratio (we used the same ratio for all 5 wheels), part of it was how uneven the floor of our shop is, and part of it was just that H drives need some tuning to make that middle wheel worth it. In my opinion, it's worth to either have 2 center wheels, each with their own CIM powering it, or put two CIMs in the gearbox you have. Either way, figuring out a way to actually get the weight onto the strafing wheels is crucial for effective strafing.