I suspect that the only approved (read "legal") plate is the one issued by the DMV. I am not aware of any regs on the angle required, so if I was forced to mount it, it would be at a severe angle to minimize radar reflection back to the source.

Umgang.......love the oil cooler ploy. Clever, very clever

I agree re the angle. My point is that you (or your lawyer) would have to read the statute in your state carefully to see if a plastic replica is legal or not. It very well may be.