For those of you in the ultimate pursuit of the most aero number may run into a section of the number that just won't lay flat. Don't want to waste a whole square for just that edge? At the race without scissors handy?
One option is to using the tearing method to reduce the size of the square for smaller edges. Simply crease the number along one of the directions and tear along the crease. Next, and this is vary important, is to lift the liner from the factory edge, and lift towards the torn edge. You might see some adhesive stretch but if you pull slowly it will all stay on the backer.