That assembly looks nice and robust, and heavy. That is 1/4" aluminum side panels, right? Any reason why you decided to run two different motors on the rollers, instead of driving them both by the big CIM? Overall, that should add some great functionality to an already strong drivetrain.
It is .20 plate for the sides, and we used two separate motors to run the rollers so we could have independent control over them. If we run the FP roller backwards, it feeds the balls to the Minibike roller at a slower rate, which gives us more accuracy when shooting from afar.
Also, the added weight in the front helps to keep us from doing too many wheelies.