Very nice Fox, looking forward to this after my EVa build got hit with a N7 mine
I'm seriously thinking about doing something like this too. I don't have any experience though, which leaves me asking a lot of questions. The main one at the moment is how do you get those dimensions for the helmet? How do you tell what length, width or depth you need to make it realistic (and fit your head)?
I don't know so much TheRabbit. I have seen lots of builds where people have sanded just fine. Now if they could just show us how they do it with out the stupid fraying! I have done some sanding and it seems it's the foam density that is a key factor. I have ordered my foam from different sources and they all seem to have varying properties. I had a go at sanding some of DBmikes foam and it was perfect for it where as mine frays like you mentioned. I guess it's trial and error foam testing till you get the right stuff. I think from what I have seen its the dark grey foam that seems to be sanded by the experts.
I've got a guy who does Gundam and EVA units for cosplay. He has a very good method for doing it, if you want to take a look.