[LLogan]

I'm going to try and keep it simple...:

ChiefDelphi as a whole will strongly suggest that you power all of your wheels. Your tractive force (pushing power) is dependent on your force of friction and thus normal force. If a wheel is contributing normal force but not powered, its weight doesn't get transferred over to your pushing force. I probably explained this in a really inelegant way.

Are the two center wheels dropped relative to the outer ones? I.e. if you take a tape measure and go from the center of the left most shaft and the center of the right most shaft, is the middle lower?