It would have to be a pretty thick coating to keep the cops from being able to see it while in persuit, with lights on. Cameras are another story, but unless you really are planning on robbing a bank, I think it is unlikely for that to come up, but I could be wrong.
Here is St. Louis, I've found that "who" pulls you over is almost as important as "why" they pulled you over. I have been given some very unexpected leniency and also been ticketed for things that are questionable at best.
In the past, I never would have done anyting to "give them a reason" to pull me over. Now, that I really am an upstanding citizen, I'm not as concerned about getting puled over, but I am still polite and keep my attitude in check.
I could see the situation going a couple different ways, the cop could pull you over and make you remove it right there in front of them. They could also give you a ticket. In which case, I hardly think it is worth it.
My suggestions would be to
A) Get anohter cover and put a lighter coating on it
B) Instead of getting the one tinted black, try one tat is tinted blue and put a light coat of night shades on it to try and make it more Navy
C) Try to find a "specialty" plates that matches you car better (Kids First, Race for a Cure, Conservationalist, etc) That $25 fee is less than any ticket you'll get for the spray.
Good Luck