I added the "skull" part of the helmet. This I made out of half a nurbs sphere, which I pulled some CVs on, then I drew a curve in the side view and projected the curve onto the surface and trimmed it. I did that twice, first to cut out the space for the face, secondly to cut out the portion for the neck.
I learned how to use "make live" effectively from this. After I made the skull portion I had a gap between the skull and the visor pieces. So I made the skull live and snapped the vertices from the visor to the skull, making for a nice fit.
I still have the skull as nurbs. I'm not sure if I should convert it to polys, I don't know what I would gain from that. I plan to keep textures simple when I finally get there, if I am not already sick of this model by then of course.