A simple approach, which yields nearly all the benefits, is to forget LOP and just use
peak EGT.
Around peak EGT, the combustion is stochiometric i.e. optimal, and since power comes from burning juice (gosh, really?) once you are stochiometric, there is no way (to a first degree approximation, anyway) of getting more power for the same fuel flow.
I fly at peak EGT all the time, and don't bother with LOP. LOP is very sensitive to the exact balance of intake air distribution and other factors.
The exact setting is not critical because the power curve is quite flat around the peak EGT point.
Lyco authorise all (I think all) their engines for peak EGT at 75% of max rated power or less. So there is nothing dodgy about this.
Obviously the over-riding thing is all this is cylinder temperature management so one can use peak EGT only in cruise, at cruise speeds.
I wrote
this up a while ago...
The benefit of LOP relies on second order factors... the lean mixture burns slower, which suits low RPM (less friction losses in the engine) because one is stuck with the fixed ignition timing in our engines. One gets about 5-10% more MPG at say 2200rpm than at say 2500rpm. But if one can fly peak EGT at 2200rpm then the gain is really small. I did very careful flight tests, where the TAS was held constant (i.e. constant thrust) and could never achieve any MPG improvement using LOP, over peak EGT. The measurement resolution was about 1%. Most people who fly LOP are getting great MPG gains because they end up flying
slower 