After many tests with some lipos. I calculate that mavic pro load current of about 9 ampe/h with stock battery in P mode. And for every 65 g incremental, the load current increases by 1 a/h. So with 2 x 3.6 ah protex lipo + 3,8 ah stock battery will have total of 11 ah. Battery's weight which increase is 221 x 2 = 442 g, so load current increase 442/65 = 7 ah. So total of load current of your mavic about 9 + 7 = 16 ah. And max flight time is about 11/16*60 = 41,4 minutes with 0% remaining capacity. I don't think it can get 48 minutes flight time.