FIRST off,
if you need any help with G-Code programming or machining in general just hit me up...
I'm wondering... does that 64:1 gearbox with the mabauchi motor have enough torque to turn the wheel under load?
A suggestion to save weight, for 1/8" polycarbonate you can use a large pop rivet to save weight as well, not to mention the higher population of fasteners will more evenly distribute the forces on the stiffening plate over a larger portion of its perimeter.
Very nice lightweight design, have to say, amazed that all those gears for four wheels only weigh 35lbs.
-q