Are you saying the Perspex plate sits proud upwards of the plate mount, meaning the hook bottoms of the rack est on that edge? photo might help, I have no problems using mine, on occasions its really useful, but I use a short number plate, old style, with a metal edge on it, raised letter style. Tippers cut the plate to short length beautifully. I wanted the old style retro plate to go with my old style car, I remember the first thing I used to do when younger was put on newer Perspex plates, but this was a nod to the old days. https://www.tippersvintageplates.co.uk/phdi/p1.nsf/supppages/tippers?opendocument&part=5