Please remember that O.S. is making recommendations based upon testing in Japan. In our discussions with them, they acknowlege that the engine will run quite nicely on the smaller props that allow it to turn between 11K and 12K RPM. They also mention that the noise level becomes unacceptable. Japan and Europe (and likely other places) have fairly strict noise restrictions, so the larger props help keep the noise down...a lot! Go with a lower-nitro fuel and the larger props, and you'll find the engine won't have an overheat difficulty.

Propping the engine closer to 10K will also make it less-suited to the 3D-type of flying that's so popular in the U.S.