CP I think with a bit of downhill you may be able to get the APC 6 X 6.5 to unload, I think the plane is clean enough. I would even try a 5.25X 6.25 stock apc as well it almost worked on a 58 oz plane. Figuring your plane weighing in just a little over a pound, and half the wing area of the stingray, it should be an interesting as far as speed on your plane. That prop would only load the motor enough to draw 635 watts at 26,700 rpm (.84 hp) so it might be an option to try.
As far as nitro I think I would try reducing the thickness of the head gasket first after reading about them wanting a 13:1 compression ratio for no nitro.
From what I read is they use thin oil and a syringe to measure the volume of the head at TDC and then calculate the compression after having measure the actual bore and stroke to determine the actual compression ratio so they have a real idea of what it is.
A couple caveats: these guys were really into fine tuning the engines, and they were not worried too much about the idle.
Last edited by iron eagel; 04-07-2014 at 08:48 PM.