RE: first flight good, second flight BAD.
Enya 40 ss - prop 10x6. The same prop we've been running on 40's since the 70s. I've had a stack of enyas in my time and none have been upset at using FAI fuel until now.
OS 46 FX prop 11 x 6. These engines are relatively lightly loaded, which does not account for the excessive heat.