Thanks for the input everyone. 
Ill hit up trooperbay and check out the visors there too.
Rafal, I didn't have the inner surface cut out when I fist misjudged the outer surface/mask size (pic of helmet with armor), but it is in the final product. When I cut out the inner surface template, that's when I had my "Oh... Well I'm an idiot..." Moment, and realized the helmet would fit fine lol.
Since I'm not too keen on fiberglass and resin, what about straight up bondo, and polyurethane coating before painting? The cardboard/posterboard I used is pretty strong on its own. Id say its as strong as a standard cardboard box, but doesnt have those creases, flexes better, and is about as thick as 2-3 sheets of posterboard. I figure I shouldnt need too much, just enough to solidify the helmet a little more, like at the back where there's only one layer of the cardboard/posterboard.
