Yay Halo!
Curious though, have you taken a look at using EVA foam for armor building? Take a look at that, you might want to consider it because personally I've always found Pepakura files quite daunting to assemble, fiberglass, and sand down/refine.
Personal favorite is Sean Bradley's Halo 4 MC build:
http://www.therpf.com/f24/halo-4-master-chief-done-156872/
But anyhow. Good luck! Hope it turns out preeeettyyyyyyy