pic: 4464 Preseason Drive WIP

It appears as if by delegating that much room to your wheel wells as well as supporting them on both ends that you are offsetting the advantage of the inverted CIM setup, and in the end are saving less room than possible. I'd actually argue that you would open up more chassis space just by having cantilevered wheels and non-inverted CIMs, which will also bring a lower CoG, and make maintenance far easier.

To answer your question, 1/4" plywood makes for a quick and excellent bellypan for those who want to save time and/or do not have the resources for a machined aluminum one. It can be argued that the aluminum ones provide more stiffness, but if you design your frame right the plywood will be perfectly acceptable.

Another question I will have to ask is why you chose 6 CIMs. Do you have mathematical proof of the advantages of the other two motors that you personally have done, or are you going off the anecdotes of other teams? I'm not saying 6 CIMs are a bad thing, but having once been a part of the hype that is built around them I now only design 4 motor drivetrains because after doing the math countless times I haven't found any advantages that outweigh the potential disadvantages.