Well, it actually worked a little better than I thought it would. I think the trick is going to be securing the gasket material properly and keeping the router moving at its best possible speed... This seemed to make a nice cut in 5 layers of .040" gray PVC shower pan liner and only started to melt up a bit when I had to slow down. You can see what I mean in the video.
http://www.youtube.com/watch?v=vNak89NKTDw