I find that the wheel trim from DALE'S CUDA SHOP is the best to work with. You won't get a 100% tight fit, but you can get them darn near perfect. I use a double clamp method (with rubber jaws for woodwork) with self-drilling screws.
I don't think they fit 100% tight from the factory either.

Mike, you had me going on that emblem thing...I was asking around every expert I know...