Any way to make a home made flange tool?

I'm doing a rear quarter panel patch on my 67 Barracuda and the back of the quarter curves up behind the real valance. The factory has it flanged behind the valance to make it look as sleek as possible (still not very sleek) and I have it fitted up in there but it's going to look kind of goofy if I don't flange it. I only need to flange it a few inches to get it to look the same as the other side but the problem is that it's curved there so I can't beat on it with a hammer.

Eastwood sells some flange style vice grip crimpers for $30 but it's hard to justify spending that much money to crimp twice and be done with it. Do you guys have any ideas for a DIY method?

Crappy harbor freight vice grips with the teeth ground down

I made a pair from some old vice grips, and some steel welded on.

I milled a aluminum block so it has a step in it, use a hammer to form the metal.