using yr head for the initial shaping will give you guys some great results.

quite a while ago i used those kevlar army helmet liners w/ hockey helmet guts glued and mounted inside. camo of course.
i now just use the closest size batters hat w/ the ear flap cut off,some trimming, mounted backwards w/ appropriate hockey guts inside.

some hockey helmet padding is really great, lots of foam, fairly uniformly thin but with multiple folding lines. i would sure suggest you guys make the shell and go to any 2nd hand store and take yr pick of lining and all fittings/buckles etc for only a few bucks. like the lining will fit just abt any helmet shape, trim the edges if necessary and you know the foam is appropriate for big hits. last one for me was $10 for the cap and $2 for the hockey helmet.

the other real advantage to the thin form fitting foam w/ a completeshell helmet is they dont catchmuch water on roll, and combined w/ a thin fuzzy hood they are real good thermal protection.

any way some thoughts on how to quickly and cheaply make a pro looking fitout helmet from yr shells.