Don't get me wrong, I wasn't knocking the idea of the wing. I'm certainly not an engineer but you look at the spoilers and soon-to-be-wings on NASCAR's COT, top fuel and funny cars, and think of the wing as a stabilizing and rear down force item. In order to obtain the speed it does, I assume down force is sacrificed for aerodynamics.
Or, like Rick said, maybe too much down force on the back would make the front end tend to lift. It'd be a fun ride none the less! Dale