Attached are pictures of the hinges I have built. They are basically Bearhawk style wing side (spherical bearings go in the holes) and RV-10 flap side. I rounded the front of the flap itself as you mentioned. So you wouldn't be concerned about the torsional loads on the rear spar from the bellcrank itself. (Which I will have to double the arm length on the flap side while keeping 4 inches on the cable side) I like the idea of simplicity. I feel that I could probably set the hinges to transfer the loads across the hinges as they will only be 1/2 inch between them.
Man, you are flat going for it ! Awesome.
If you could get your hands on some scrap spar pieces, I think it would be worth your while to mock things up. I buy wrecked wings for parts and keep the straight part of the spars. I like to build a mock up and leave it hanging on the wall for a few days, so I can pick apart the faults of my new design.
A slight critique on your welding procedure. Start welding on the end of the V with the gap. Build up some weld on each side of the gap until it almost touches. Each buildup should be allowed to cool to room temp. Tack both ends of the V and let that cool to room temp. Weld from large gap side; letting it cool in several stages. It will warp a lot less.
Doubling the length of the flap side of the bellcrank is going to double the force on the flap handle. Are you doubling the length to get more flap travel ?
Again, AWESOME !