We get asked all the time about block style 90* adapters vs the bent tube versions. The bent versions are just slightly longer than their block style cousins, and probably could be made to the same drop lengths. While it is true that the bent tube version will 'probably' flow alittle better ( I just got these and havent tested them, but common sense says yes), I personally have a pet peve about them, especially in aluminum. The bent tube versions in the pics are from Earls, a very respected fitting supply company that I'm sure most of you have heard of.
They made their name in the racing game, from drag cars to Indy cars, so surely they would be fine on your experimental plane. My issue is the brazed joints between the ends and the tubes.
The dark colored area at the tops of the ends is the heated braze flux left over from the brazing process. The flex is generally mixed with the aluminum powder and spread at the joint, then heated by generally a 3 torch machine so the joint gets equal heat 360* around it. Its on a timer, and when the little bell goes ding (10-15 seconds) heat is removed, and coolant is sprayed on the joint. Yes, pretty strong, but I dont feel its as strong as the block style, with no brazing.
The machines take most of the experimentation of time and heat out of the equation. Back in my industrial days, we used acetylene and fluxed aluminum rods to make a/c fitting repair. Took LOTS of practice. Now is is less expensive to make the bent tube fittings, other than the labor involved, but you'll probably find they are more expensive, at least these examples were.
Eventually, I'll run a flow test on these for comparison. Might be a bit---got this OSHKOSH thing to attend.
Tom