I have a 7"x6" in mine. Obviously it hangs a bit lower than the bracket, but the back of the number plate is black and isn't too noticeable. The font is very close to the legal size and i haven't had any trouble with it yet. I ordered from here: http://www.platecreator.com/
we can see that the french licence plate is slightly above and below bigger.
something we make: black paint on the back of the plate.so it's more discreet.
there are license plate manufacturers that make "tailor-made".but here it is a fine 135 € if you have an unregistered plate.we play we win or we lose .. I decided to play ..
one more thing: it's not my bike on the picture but that of a client of my concession.