What material/size is plate the gearboxes are attached to?
This chassis concept is pretty similar to what 3467 ran this year. We liked the kitbot concept but disliked the side plates because most of the hole patterns were pretty useless to us. Additionally we weren't huge fans of the slim drive channels as it made it hard to integrate Colsons. So we CNCed our own plates out of 1/8in Aluminum and placed a lot of evenly spaced .188in holes every inch to give the design groups plenty of options for mounting and the ability to choose what size hole they needed. We mainly drilled the holes out to .25in for 1/4-20 hardware which we have unofficially standardized to. I know its overkill but every team has their bad habits.
Overall it was probably the best and most reliable drivebase I have ever worked on in 8+ seasons. Evenly spaced chain runs, color coded spacers, and identical wheel + hardware on every wheel made assembling two robots a breeze with every last part interchangeable. I think we had to swap the center wheels once during 6 events but other than that it ran like a dream all year. Still have good chain spacing.
In terms of strength it held up very well but we went with an 8 sided concept so bolted on to the left and right module was a large piece of U-channel that the bumpers attached to and gave us 3 faces on each side (as seen in the bottom picture). This provided a decent amount of extra strength on our sides but if you design your bumpers right you can make your drivebase frame stronger without using the robot weight for it.
If you want I can send you the .step file for ours.
