The way we were working it up, I had an outer shell, and then an inner shell that both cradled the retracted visor and also separated the wearer from the pivots/electronics/and so forth... Ha I got excited to think we could cheat and just build 'over' a helmet, but that's OK. If it was easy, everybody would have one alreadyFor clarification they did not use the Porsche helmet. I believe the helmet was scratch built. I just think that is where they got the visor. It is the only visor of that type that could have worked, short of military flight helmets, but those are not wide enough I think.
Let me get some pics up of the shell, modern sun visor I am using, and the Porsche visor in the next few days.
I do like how that temporary visor looks in the shell, the curvature looks great.