Originally Posted by
gooba
I know very little about the airflow underneath of my chassis but I have to think that gap then a wall of lexan has to hurt the aero.
It does. Reason why Oval bodies have the back "wall" fully cutout. Sure it looks much less like a real car after that, so most rule books forbid it for TC- and
a fortiori for VTA, I would assume.
Personally since I don't race much, and only on club level, I just ream out two or three holes at the top of said wall, right under the wing, so that not too much air gets trapped and fights the downforce from the wing.
I have no idea if it works but it helps me sleep at night. If someone ever complains about it I'll just put a piece of tape over the holes.
That said, you could try to add a thin lexan sheet between the back of your car and the bottom edge of the back wall. It would probably be legal and possibly minimize the parachute effect. Let us know if it works !