My 1st sumo

This will be my 1st attempt at a sumo style bot/RC. My design stems from Deadblow (http://www.lazytoad.com/teamtoad/season2/deadblow.JPG). Although it wont be as refined or visually pleasing (due to the lack of machining equipment) it will be powerful. I am planning on making it from 3"x1/2" 6061 Aluminum for light weight and strength. I will be using 2 Black and Decker 14.4v motors and gearboxes. It will be a chain driven 2.5:1 ratio from the @500-600 rpm outputs to 4-7/8" wheels 4 wheel drive. Top speed should be around 20-25 mph. Im planning on using 18v Li-Ion Makita battery for the power. I plan on using BaneBot 4-7/8" wheels 2 per corner. If those crumble or disintegrate I will have to find some good sticky casters to use. 

Overall size should be 12"x12" square 3.13" tall (without wheels.) I also plan of having it be able to run upside down with the driveshafts centered between the top and bottom. This will give me a little less than 1/2" ground clearance. Weight will be between 12-15 Lbs (I think).

I dont plan on any competition with it, its just for fun. I want it to be able to carry about 200Lbs but thats being hopeful. Initially it will be RC controlled, if and when I make it autonomous I hope to haveit be able to track moving targets. 

It will be powered by a PIC16F887  written in C on a custom board. The motor drivers will be 260A Mosfets I have laying around with industrial relays for polarity switching. Ive just blown up so many H-Bridges in my proof of concept design, plus the complexity of an H-Bridge is unwaranted. I will post my proof of concept design in action soon. Its a single axle belt driven platform made of wood (frankenstien).

Any ideas or changes anyone sees in the Cad drawing let me know, Im not proud and am open to any suggestions. I hope to have the parts ordered this week.

If anybody (chris?) has any advise cutting and boring large holes (.665") in aluminum let know, I have no drill press :( and  pretty much just a hack saw and hand drill to work with. I may get a metal cutting wheel for my mitre saw, we will see.