Thanks, I never thought of that, having done that trick of flipping lids myself, I think youre absolutely right.I had an air cleaner once that had a lid with the center bubbled in it like on the right. It was on a car with the lid flipped upside down and screwed down with one of those "washered" wingnuts. That is somewhat the result of doing that...
with the lid flipped upside down
Good for 20 Horsepower!!having done that trick of flipping lids myself