[MrForbes]

The trailer wheels are near the center of the trailer, so it won't have a lot of tongue weight. You can position the wheels on your robot wherever you want to, they dont need to be exactly in the center. You can position heavy parts of your robot wherever you want to, so the center of gravity need not be in the center of the robot. What all this means is that you can balance the robot how you want...you can have a 6 wd robot that rides on the front 4 wheels almost all the time, if you so desire.