I had a long-time Chieftain engineer tell me that he will not set the density controllers to provide more than 40-42" because "If your pilots have a cold day they will blow the pots off".
Never heard that one and if I did I would refuse to fly the aircraft as any single engine performance will be woefull. Correct power adjustment for the Chieftain for full power at sea level, ISA conditions would be around 43 inches. Not many places in Australia would come in under ISA conditions for most of the year.
Setting 40 Inches is effectively running the engine at 95% power at full throttle and that's if its ISA. ISA+ and who knows how much power you are losing.