I prefer a hood scoop over a hole in the windshield. Just do that or use one hole at least an inch. I like to cut scoops they look much better. My revo has a kind of backwords moonroof on it, very effective.
I put a 2 inch hole in the windshield of all the bodies I run on my RS4, in line with the cooling head. But I also add some holes to the rear window as well so the air can pass through better.