[Christ]

I think (don't know, but think) the amount of energy used to send that extra little bit of air out and around the airdam (which is designed for downforce) is probably a losing situation when you could have just let it go under the vehicle.

I've been told (never verified it, don't follow NASCAR personally) that the NASCAR body cladding and wheel designs are used to create low-pressure under the car specifically to use pressure differentials (over versus under) to keep the vehicle on the ground. (Another downforce consideration). I'm not entirely sold on this, because it sounds too much like a mis-application of Bernoulli, the same one that schools still teach as being what makes airplanes fly.