so I guess Ill skip the inertia and friction rant . . .
This is near impossible to calculate since it involves friction . . . friction and inertia is what will cause the body to spin with the servos. But I think that if you use very large diameter wheels, and keep the weight as low to the ground as possible, you will maximize the moment arm length. Basically you want:
force from moment >> force from friction and inertia
Use a wheel diameter of perhaps 6" or greater, and keep the batteries/electronics like an inch off the ground, and I think it will work. Would be interesting . . .
Expect it to wobble/swing during stop and start motions, so you may need PID control
on it to have the speed slowly ramp up/down.