Years ago I hung out at the top end of our local track and watched the cars go thru the lights instead of watching at the starting line like I normally do. The cars that went over say 120 you could see on some cars with 'glass hoods that the air was pushing the hood up or down a noticeable amount. One guy had a purple 70 Challenger and the front middle area of the hood would lift up a bunch. He really needed to block off the grill opening with some clear lexan like some do, or add another pin in the middle as it was flexing the hood way more than I would be comfortable with.