When I got pulled the bill(motorbike cops) actually measured the width of my rear number plate digits, and then tried to read me the riot act as they were 2mm too narrow, legal space and all, std font etc etc just 2mm too narrow, yes he did have a 6" steel rule which is std police issue!!
I still have not changed it and won't while there are others including his son going around illegally spaced/illegal font etc, would rather take my chances in court.
tabetha