[DampRobot]

Have you considered how your corner gussets will stand up with significant torsional loads? Or are you using a bellypan? Also, how will you make sure that the two sides of the drives are parallel? Rivets holes usually have enough play in them that locating of them doesn't work super well. Are rivets the only things holding the frame together, or is the tubing welded too?

I only ask because I've recently been working through some of the same design problems myself. It's interesting to see how different people have worked through the same problems.

By the way, I really like those bumper extension tubing thingys that surround the center wheel.