I should have a visor later in the week to help with the spacing. The dome of the helmet is ceareal box cardboard coated in Pollyfilla (wall plaster. The rest of the helmet is shaped 12 ply poster board. It's about 3mm thick and fairly stiff and a heck of alot cheaper than Sintra. A 36 X 24 sheet was $6 CDN. vs $50 for Sintra.
Did you seal the dome and card sections with anything. I used Exterior PVA which not only waterproofs the thing but plasticises it too so you get a nice hard surface which actually take paint well. On the whole I agree, with placing the visor oin or at least something to help keep the shape whilst painting it. I think you've done a fine job on it. Scratch building's a hoot.
I thought it was a high price to, but the nearest distrubutor is 2 hours north of me and the only sign shop that would order wanted $40- $50 for a sheet. Next time I am in Calgary I will grab some but for now the board works great.