Yeah-ha! Someone else who's going the regular printer paper approach.
I did the same thing for my JediFraz HALO 2 Mk VI helmet (still a WiP), but my medium of choice for the finished product was sheet styrene, approximately 1/8" thick.
All I used was regular printer paper (didn't have any 110-lb cardstock at the time) and low-tack painter's tape (the blue stuff) to keep it together.
Then I applied the styrene panels (cut out based on the geometric surfaces of the Pep file) using a Uhu Industrial Strength glue stick. Pretty heavy stuff to be layering over a regular-papered model, but it held together amazingly well.
After that, I then puttied the seams, sanded/rounded out the sharp edges and angles, and have got it looking pretty good at this point.
I have to admit, I was rather impressed with how well it worked out, given what I was working with.
And I can see you're looking to be on the same track with yours. Of course, the model you're using has next to no sharp edges or angles, so that'll make your job a lot easier, lol.
I like your method for how you're assembling the helmet, in terms of materials used. Definately unique amongst the other helmet builds I've seen. Helps to set yours apart from the rest. Original.
Way to be different, dude! I look forward to seeing more