Jim, actually the first Atlantic was made of Elektron (a magnesium alloy) - which was either impossible or extremely difficult to weld (at that time). The other three bodies were made of aluminum but since everyone liked the 'riveted seam' they stuck with it.

By the by, if I was making a split windshield, I'd use raised metal both inside and out. Yes, you could look down the edge and see that it was a fake divider, but it would have the split window look.

Biba