Afternoon guys...
I think it is called "spline", but am not quite sure. The tool that looks like a pizza cutter is a spline tool hence the name. You can also get canopy trim from tower or maybe the LHS has it. Here are a couple of examples:
http://www2.towerhobbies.com/cgi-bin...?&I=LXG866&P=7
http://www2.towerhobbies.com/cgi-bin...?&I=LXG867&P=7