Effectively, the Cessna charts give you pressure altitude up to 8000ft at max weight. ISA at 8000ft is 0C. So my C182 p chart runs out at a pressure alt of 10500ft for max weight. If I lower my weight I can get p charts to
ISA+40 or 13000ft pressure altitude. I have never operated in PNG or West Irian but I am pretty damn sure any pilot who has flew up there can tell me that a C182 can take off from 8000ft pretty well.