on the headrest. I did the same thing and carved one out of balsa. I HATE plastic on my planes. So I did the same thing Jspencer did and carved it from balsa. After you get it carved use a dremel to carve out as much of the inside as you can. It will make it easier to mount, and save a small bit of weight.

on hinges. On my Hog I used CA hinges and then I sealed both sides of the gap with monokote. I've gone away from using CA hinges now (I use Robart hinge points now), but I still seal both sides of the gap with monokote.