That's good to know, I was thinking about buying some new ones if I don't paint my old ones.
When having run into that problem before there are a few ways to solve it, scissors or tin snips can work well if the material isn't too brittle, a dremel with a grinding stone works but usually leaves lots of little bumps that have to be sanded flush. The best method for me was a belt sander, a hand held unit mounted upside down in the vice or a bench mounted it doesn't matter, you just use the leading edge of the drum to remove the material, so your panel is on an angle (tangent) and you move it in one smooth stroke in the opposite direction to the rotation of the sander.