I put a fiberglass hood scoop on my pontiac using the method in the instructions (fiberglass, scoop, anouther layer of fiberglass). it was perfect for about a month and then a zig zaggy hairline crack appeared all the way around it. I took it off and tried just using body filler. same result. then I tried rivets and body filler; no good either. then I tried a plastic scoop and it has done the same thing. a friend told me the problem is I need a metal scoop to mount to a metal hood. is this true? before I do it again I want to know what I did wrong. or should I just take it to a body shop, although I'm not sure what they would do different??