Hi guys, nice robot!
[OFF topic]We tried contacting you by the school phone today but nobody answered

[/OFF topic]
There are three things I'd suggest you to try:
a) Leave the high traction wheels in the heaviest part of the robot and switch the other two with a pair of wheels with a smaller coefficient of friction;
b) Chamfer or fillet the corner of the wheels (that's what we do to our treads), that really helps a lot. This is a picture:
c) As Joe Ross pointed out, try changing the gear ratios for your system. It may be a little late and it's definetely the hardest mod, but it'll work for sure. Plus, your circuit breakers will thank you
