This is where a lot of the problems could be fixed.
modify the baffling to get an even spread of CHT's (illegal if 24 reg) and fit fuel injection (again illegal) or possibly re-jet to run really rich (25-30 L/hour at 75% power).
The cooling air distribution is something very few understand at all.
Fuel
DOES NOT COOL, it delays the Theta PP and lowers the ICP. Hence a lower CHT.
This is the wrong way to cool an engine.
I reckon cooling issues and distortion of heads as a result are 45% of the problems, and the result from running far too rich the other 45%. 10% could be any number of things. Just shooting from the hip.