had my old car (living in IL then and it was illegal both spots), I was never pulled over for it.
I was written a warning for it when I was pulled over for speeding and issued a ticket for that, but I received a call from an atty friend (which I didn't call him first, he must have seen it coming up in traffic court) that the speeding ticket was "lost".
Kept driving that car (Honda Civic, so it blends) with the plate and nothing else ever happened. I might still have it somewhere.
Now I did have an ND Alum frame on my back plate. No one (even the cop) said anything about that.