If you were to load up a Navajo and take off at 40C lose and engine and injure several people you will then be under the microscope, as the injured will want a ruling of who's responsible under law. Piper is going to claim you were outside the operating envelope for the aircraft, as there were no charts to prove you could climb.
The manual has the necessary charts. Makes me wonder how airlines managed to operate the aircraft in +40°C temps as occurred in South Aus, hottest I experienced in Whyalla was 49.4444°C.
