RE: JBA .56
The rpm on the 12.25x3.75 was with the Jett tuned muffler. For some reason (I was probably too lazy) I didn't take muffled rpms on 12" props on the 55AX.
I also noted that the JBA seemed to not respond to the tuned muffler as well as the OS, milder timing, in my opinion. On the two 11" props, 11-6 APC & 11-7 APC, the JBA, with the stock muffler, was equal to or a couple hundred rpm beter than the OS.
I have a second OS .55AX new in the box and also my own JBA .56, so I'll do a second, but shorter test on those two.
The JBA .56 weighs, using my digital scale, 18.4 ounces. As I recall, the OS weighed 18.3. Both of these are with muffler. The interesting thing is the JBA muffler weighs a ton, coming in at 5.3 ounces. This is even heavier than a Jett tuned muffler. The bare engine weighed separately is 13.1 ounces.
I did run the JBA on the bench at 1/2 & 1/4 throttle, then hit full power. The engine went up smoothly. That still doesn't tell me what it'll do in the air. I have a Goldberg Wild Stik with an SK 50 on it. I think I'll remove it and mount Ed's engine for a quick flight test. The Wild Stik can't use full power in level flight because of the wide controls (Ail: 4", El: 4", Rud: 6") and the chance of flutter. It's more of a high wing 3D plane like the Heckler I used to fly. It should be a good test for running at partial power.