Ok, i feel better to have got that off my chest.
No i have not flown in Botswana, yet. Have you flown in the altiplano of Bolivia? This game could go on all day, so i will stop the p!ssing contest and accept that you have significant Hot and high issues, but i will say that flown to the correct loading and power speed configurations that it will do better than the 100 fpm that you claim at 6-7,000 ft. You may be back around 200 fpm at 9k, but at correct weight. Overloading will certainly diminish performance, the skydiving operators here in aus have proven that. All that space just asks for more bods, but there are limits.
I will pm you when i visit africa and we can have this chat over a beer as it should be.
Posted from the cockpit of a TC 320 airvan in cruise somewhere in the lucky country. Am on trans continental flight at the moment.
HD