I thinkyou are way over thinking and over engineering a simple part of the Ringmaster. I have never seen a sewn hing fail, nor have ever heard of one failing. If we are talking about a 1/8" stab/elevator on a Ringmaster, if the balsa doesn't fold on a maneuver, the sewn hinge will hold. Just use good strength carpet thread. I have read where 1/2A flying line is the favorite choice. I think four decent sewn hinges on each side will out last the rest of the airplane! Barrel hinges on 1/8" balsa , no matter how neatly installed, doesn't leave much meat left for stress and strain. One tweak on a cartwheel from a rough landing and they will rip out. If you are entering OTS contests, you can't change the thickness as per the rules. If you go with the tube hinges, I would recommend a slight gap between the tubes. Space them with little bits of paper or card stock that can be torn out after assembly. Sitting in the sun, you may be surprised how much they may grow and bind. Dust and dirt will get in no matter what you do, and a decent gap will allow it to work it's way out also or allow you to clean it. If you fly this model a lot, I will be interested in know how much vibration affect the wire/brass joint and if any metal gets hammered and they get sloppy over time.
Type at you later,
Dan McEntee