RE: sheet balsa hinging techniques -how do you do it?
Monokote over and under hinges. I've used them on many models up to 25 size over the years with excellent success.
I've also used the CA mylar strip hinges on 1/2 A's as well down to 1/8 thick. For the small ones like this I cut them in half so they are only about 1/4 wide but full length for less resistance but good gluing.