Youre lucky if you are only after a few more minutes as I need 20 minutes for our mains so need low KV motor and 5 or 6 cell batteries.
Doing my research if you wind the timing down on youre ecu to about 7 degrees and gear down and drop youre epa on radio down plus be careful with youre finger
and maybe drop the lvc on ecu to say 2.9 volts per cell you can add a few minutes onto run time.