I know you have it on already riveted on, but I will throw out what I had experience with. When I was younger I had a car that I put a scoop on. Riveted down, used filler to smooth the transition, looked great when it was painted. After a while it cracked. After that I did some research and found that the best way is to sand the hood to the metal, sand the bottom of the scoop, put down a layer of fiberglass filler and then attach the scoop to the hood as planned. This procedure will help to keep it from cracking later. Not sure if its a for sure option because I sold the car before I could try it, but that is what I found out.