Helmet base support help


New Member
i took a skateboarding helmet and took the plastic covering off so its just the hard foam base thats the perfect size for the pep pieces. now what im doing is constructing the MC helmet around the foam base like the diagram below and plating it in thin, sturdy cardboard, BUT what do i put in the empty space between the top of the foam base and the actual MC helmet? should i fill the empty area with caulk or something that will be easy and sturdy but will not in any way warp the shape on the helmet? what should i do?


(obviously this isnt to scale. its just to show what i mean)