Our team also uses 6 wheel drive with all traction wheels. The center wheel is dropped slightly to increase turning ability. If you do not drop the center wheel you will need to run the robot with a lower gear ratio to enable turning. Unless of course you run with a ton of motors in your drive train. The other option that a few teams use is to use pneumatic cylinders with delrin blocks or small rollers on the end at each corner of the robot. When they turn, certain cylinders fire allowing the robot to skid during a turn. When the turn is done, the cylinder retracts and you are at full pushing power again. I think Wildstang has done this in the past. Good luck with the drive design.
