Depending on your local law enforcement...
For my 1999 Contour SVT I placed the front (required in WI) license plate up in the front windshield, stuck up to the passenger side of the rear view mirror.
Had it there for 13 years.. 100,000 miles.. Several speeding tickets in those 100,000.. never a comment from ANY officer about my front plate.
Now I am also an old lady.. so maybe for young guys it may not go so well?
The top of my front plate slide up under the liner. and I cut off the bottom below the numbers.. So it really was sort of like a sunvisor...
Only ONE person ever commented about it, The dealer where I bought my new 2012. Which was out in the countryside.. vs my living in the 'big city'..
My new 2012 front plate I have painted it black with just the letters/numbers visible. So far two years like that no comments. and I know several cops have glanced at it without saying a word.
(I have indoor parking, and have to wait for the garage door to close, plus it is on a busy street, so cops have been stopped for the light, looking at me sitting waiting for traffic to clear etc with my front pointed at them...)
(I guess cops around here have more to do than annoy trivial law scoffers..)