[Cory]

I don't really see where the debate is. It will turn best if the weight is on the back, because it's helping to lower the scrubbing forces on your front wheels.

look at it from the perspective of a dropped center 6WD. If you have the center wheel on a 38" long robot at exactly 19" and your CG is forward of the center wheel, then your wheelbase is 38" long, plus the distance from the trailer axle to the back of your robot.

If you have the same setup but the CG rear of the center wheel, then your wheelbase is effectively 19" shorter (assuming the front wheels never touch the ground).

The same thing applies to a 4WD robot, or any robot with all wheels coplanar, it's just less exaggerated.

Shorter wheelbase=less scrubbing force=easier turning.