We had 1/16" thick chassis channel like that last year, I hate to tell you but the perimeter got the living #$#$% beat out of it. It caved in like a tin can, and not even in rough play. We ended up putting 1.5x1.5x1/4 angle around the top, on the front and back. That helped but even that got caved in. You might be OK if you put a bunch of noodle foam around it. Also having those wheels outside the envelope without some kind of fenders or protection might get the shafts bent when you take a side smacking. Sorry if I'm annoying you, just want to be helpful.
But other than that, this is a very clean nice design, nice light gearboxes. G/L