According to the engineer, the site and manual are incorrect. He told me he plane to correct it. The prop sizes were for the previous engines they carried. I know the engineer states in another thread that a 12-5 was the smallest prop to run.

I know Turk runs an 11-6, but he lives in Turkey and uses no nitro fuel. I would go no more than 10% and listen for a lean run. He stated that a characteristic of the prop being too small was the engine running lean after about 5 minutes no matter how rich it was set on take off. Listen, or have your instructor listen, for leaning out after several minutes of flight.