Aero piston engines are intended to run rich to keep cylinder head temperatures down
Not the whole story. We use an excessively rich mixture at very high power, to SLOW combustion (reduces the speed of the flame front), and put the peak pressure far enough after TDC to prevent detonation and keep CHTs down to reasonable levels. At reduced power levels LOP can be used to advantage. See for relevent articles (you may need to register but costs nothing)
http://www.avweb.com/news/pelican/182146-1.html