If there is less air going under a car like ours, it will be faster, usually, because all that stuff underneath disturbs the air flow, IIRC. While there is an increase in frontal area, it is offset by the fact that there is much less disturbed air at the underside and back of the car.

BTW Al, you should see the tub you sold me...cleaned and painted it looks really nice. I'll send you pix soon.