I find the sharp x-acto knife trick to work great especially at an angle. I have had some very small graphics at times, and this seems to work best. Try it at an angle. Also with small stuff, I find that rubbing a little acetone on a cloth over the area you are applying to helps greatly. This is for monokote over monokote. But I stick with the knife trick on small pieces. At a good angle, you should not poke through the covering.
Good Luck![8D]

Just to be sure we are on the right page, I stick the knife through the backing at a slight angle and it lifts the backing off of the covering. I do not try and find the edge, you will be there forever.