See if you can cut a roof section out of junk car. At least you will have the curvature correct. Then flange it in like they said. It's worth a shot.

Scott 1956 Dodge Custom Royal Lancer (408 Stroker, 4 Wheel Disc Brakes, Rack & Pinion, 6 speed) 2002 Dodge Ram 1500 Quad Cab 1976 Corvette