you should cut your rear license plate and make it flush with the bottom of the plate holder. I did it and was very happy with it, even though it took longer than it should have...
another cool trick for us D.Schwartz guys in california is to paint the number/letters on our plates black with model paint. not a HUGE difference but it does look alot nicer on the car, and it doesent cost much:) .
saw that on a white M coupe. subtle, but very cool.