Originally Posted by
Shoreboy57
Just one theory (from Car Life Mag in 1970). I'll leave it to the experts to argue its validity:
The forward part of a car roof is a negative pressure area. Venting the higher pressure cockpit air into that area would noticeably reduce lift. With a vinyl skin covering a series of pin holes, this could have been accomplished without the inspectors noticing (they tested the car with magnets). Nobody ever figured exactly why they ran the vinyl, though and finally got them off on a technicality. (The roofs didn't appear on the homologation papers.) The rules didn't say Penske couldn't use them, so his record was safe.