LOL....you guys are way overthinking these hinges. I've watched Sparky install them many times, and drew up the outline for them in his Viper plans (CAD by yours truly, I might add).
It's simply 1/8" aircraft plywood, 1" long X 1/8" wide tang, and a 3/8" diameter "bulb" on the end with a .059" hole centered that accepts a small brass bushing (
https://www.rivetsonline.com/gs2-6-brass-eyelets/gs2-6b) that in-turn accepts a .040" diameter wire.
Take your stationary stock (wing TE/stab), run it through a router to produce a 3/8" diameter half round groove centered in the
trailing edge of the stationary piece.
Use a 1/8" wide saw blade (typical table saw blade width) to groove the
leading edge of the moving stock (elevator/flap). In this groove, use epoxy or thick CA to secure a carbon fiber rod (3mm OD/1.5mm ID) the whole length (
https://alofthobbies.com/collections/pultruded-carbon-fiber/products/3mm-x-1-5mm-x-500mm. Then just simply glue in some balsa to act as a cap over this and trim to size/shape of the moving surface.
Now, here is where it gets a little "sticky". Sparky purchased a cheap Harbor Freight (I believe) bench top table saw that is about as weak as can be. He only uses it for one thing, and one thing only - cutting 1/8" wide (blade width) x just over 3/8" deep slots in the leading edges of the moving stock. Cut right through the carbon tube, as well. This produces the slots for the hinges
Now, just take the hinge, with brass bushing installed & peened over to keep it from falling out (I suppose one could also use brass tubing of an appropriate size, and simply peen it over, as well), place it in the slot, and run the wire through. It should be a free moving fit - if not, sand wherever it binds.
Line up the prepared moving stock and mark where your newly cut hinge slots are on the stationary stock. In these locations, drill a 1/8" diameter hole (same process as a Robarts hinge). Follow that up with a sacrificial hinge that has has the tang cut at an angle. This hinge will be used to broach the round hole and form it into a square hole.
Pre-fitting the hinges a few times will insure the pieces fit together very well. After finishing the entire airframe, 5-minute epoxy or wood glue can be used to secure the tang of the of hinge into the square hole.
Overall, after getting the hinges laser cut, and buying the brass bushings in bulk, the whole hinge system becomes incredibly cheap & easy. Most all of the roads y'all are going down have already been explored by Sparky, and he keeps coming back to the tried and true plywood versions. They simply work, are cheap, and are easy to do.
Steve