Been following this thread since the beginning, and yeah, my name is among the others with their jaws on the floor. Amazing work.
I too was considering how to get my big head into a properly sized helmet, and a hinge plus magnets was my first thought too. That is, of course, only if my head won't fit. Which I'm not sure of yet. But either way, I'm going to love to see how you tackle this.
(And to think, this is just the helmet. Wow.)