Max, just to clarify. A++ and C+ have very different engines, the C+ has a 2S1. The C/C+/C++ is a heavier airframe than A++ so you need to talk in terms of available payload rather than MAUW when comparing your numbers.
You might be surprised when comparing performance between an A/AllisonC30S and a C/Arriel1S1 under Karratha conditions - I stand to be corrected but I wouldn't be surprised if the A model did slightly better than a C in hot conditions. Obviously a C+ will do better, and C++ better still. I have more recent form on a C+ and from memory we could take 12 pax up to about 32 degC. After that temp you start weight limiting to make good with that crazy Cat-A elevated heliport departure profile. Being at MAUW in a 50 ft hover with no vertical performance to make CDP is no place to be if a donk quits at that point in time. If it does quit you'll need every ounce of 30sec OEI and probably a new undercarriage after arriving at the bottom.