Chris, one of the issues that I see on my car, is that the scuttle is curved, but not at a consistent rate. One way to get a correct profile is an artists and architects tool that is a flexible rod that stays where you bend it. I use it when scribing fittings like cabinets to walls that aren't flat. It is called a flexible curved is available in lengths up to 30 inches.
Erich in Seattle
Erich in Seattle