When I modded my Hasbro Voice Changer Clone Trooper Helmet last week, I looked but couldnt find a template for a visor mod to make the big hasbro visor more screen accurate anywhere,
I ended up just mocking up the visor with tape & then making up 2 visor parts from an old plastic fire escape sign to stick on top of the existing visor/cheeks,
they were just done by eye so I'm not pretending that the measurements are 100% but if you want to quickly & easily mod the hasbro helmet they work pretty well.
I have attached an A4 scan of the templates here if you print it out full page A4 they should fit fine,
Bit low tech I Know but works ok & I just thought it might be helpful for someone looking to mod one of these Helmets