AeroModder: Ah, downforce! I guess it makes sense when you think about it, like the high pressure area in front of a windshield, only to the max. I would assume that would mean the lower-drag option would be the diagonal air dam (better for our purposes).
Spydyr: Just as a side note, the general rule of thumb is that you don't make the air dam lower than the lowest part of the car you are shielding (lower at the wheels, higher toward the center).
__________________
|