[EricH]

Yes, the center wheel should be lower... IF you only use traction wheels. If I'm not mistaken, the KOP chassis has a dropped center hole. If it doesn't, I'd drill a new hole--turning a hole into a slot has a tendency to not end well if you need stuff to not move.

But there are other options. For example, you could pick up some omni wheels and put them on the "light" end of the drivebase, or on the corner spots. (Don't drop the center wheel for this configuration.) Or you could use a "wide" configuration (wheels on the short side of the chassis) which will give better turning.