Ever thought about a nibbling tool?
Not one of them manual things, but the one that either fits into a drill or the proper thing that is run by electricity or air?
I remember seeing a thing on TV here last year during one of the many Info-mercials I wake to in the morning, that gave a clean (not sharp) edge.
I'm not suggesting you buy one of THEM, but ask at your local Trade counter and see what they can do, if a guy on an Infomercial can use a nibbler, crikey, you're home and hosed!