Hi there. I would love to chime in here... I live close to Jhb South Africa and also have significantly reduced flight time due to altitude - 4800ft ASL. I love my FC40 and think its great value. One thing I struggled with was getting the P2 props to work as well as the 8 inch stock FC40 ones. The wobbling was bad and disconcerting. I reduced gains thinking the larger props were reacting too quickly when in fact they were reacting too slowly. I got the gains up at 130% roll and pitch and the craft is much more stable now.guards are great while you're figuring out how not to run into things. 9443 props are a nice upgrade. 9450 props are a great upgrade. If you're thinking about a gimbal for a GoPro or similar, you may seriously want to consider purchasing a light weight model.
I was flying with only a fpv cam and a 100mW transmitter extra and can get 9min on my 2200mAh batts and then recharge with 1850-1950mah to full.
My pain is when I add the Feiyu-Tech G3 3 axis gimbal with FC40 camera the flight time drops to 5:30 for the same recharge... so I really agree with the lighter gimbal sentiment!
If it wasnt such a technical challenge I would've loved to try 10x3.8 props and report on that.
Cheers from sunny South Africa...