The material we’re providing Josh is all being considered for Proofgrade inclusion but is in various stages of development. The chipboard is from one vendor but isn’t anything very special (unlike e.g. the 1/4" plywood, which is custom fabricated and has the protective coating).
Oh, and @jkopel, so you don’t have to waste all the hardwood… you basically need plywood or MDF to make a living hinge. We have many splinters in testament to this. 
If we didn’t get you any, let us know and we can fix that.