You're probably fed up with queries about 91 FX reliability, but I am somewhat unnerved by all the stories about overheating leading to engine cuts in flight. I operate in the UK and am unclear as to whether I should be following your US advice (ie use a 13 x 8 prop) or the Japanese advice (use a 15 x 8 for sports flying). Noise is not a particular problem for me as I fly from a military airfield. All I want is the most reliable set up. I would be grateful for your recommendation.