You should use polycarbonate. It's pretty cheap and if you have a heat gun you can form it to the stuff you have already made. A 28" X 30" X .085" sheet is just under $27 at Lowes, it's called Lexan. That one sheet is more that big enough to either do a helmet, a chest piece, a back piece, or several arm or leg pieces. And it's stupid tough. Some sunglasses are made from the stuff and can take a 12 gauge (pellet shot) at 10ft, though I don't recommend actually trying that. Then just add your eva foam as padding.