[JesseK]

I too like the I beams as use for a frame -- very creative!

From a maintenance standpoint I would make some strategic holes in the I-beams so you can see what's going on inside the modules in the very likely event of a problem.

To solve the frame perimeter issues (based upon previous years' rules), some stiff foam or lightweight plywood would fit nicely into the I-beam rails.

I'll also echo John's sentiments, yet also add to it that programming a crab drive is just as difficult as building it. Hopefully you have very, very talented programmers since they've probably only seen un-optimized or theoretical code.