pic: First attempt at Sheet Metal Chasis please give advice to help me improve

Put some braces between your transmissions, or something to stiffen the frame. It looks like I can warp it in any which way I'd like with a little impact.

Any reason for using FIRST wheels? Plaction, Colson, etc are all really nice wheels, and provide a ton more grip than the FIRST wheels.

Other than that, nice design. Keep up the good work.