Sedans need a 'donor car/van/wagon that have ribs for some reinforcement so you dont have the oil canning effect. The coupes only have about a 3'x3' hole to fill so Dave S' suggestion of a piece of 20ga (or a smooth slightly curved donor car roof) is right on the money. Ribs on an 'A' coupe top look.......like crap(and IMO, so do sun roofs). I'm seeing more with just a new vinyl roof at shows these days - and they still look timeless(to me).