[MFS766]

6-wheel is the best, but make sure the middle wheel is slightly lower (1/8 ish). This blends the 2wd and 4wd, all your weight is going to wheels with power so you should have good traction. It also centers more wieght on the center, oppose to the edges (farther from the turning point) of 4wd. This means 6wd takes less force to turn the robot. Also the wheel base is shrunk since amost only 4 wheels will be possible to signfigantly press into the ground. 4wd of the same shruken wheelbase are not stable. I saw many tip last year. Hey with 6 wheels, if it has problems, you can throw of wheels until you have 4wd of 2wd with a castor or two. It is easier to take away then add.