3Dsavage, I run a BP21 and 3S 1300 ma 12C batt and a 7X4 folding prop on my formosa, this set up flies good and gets 12 to 18 min flights at 1/2 to 3/4 throttle, you should get 5 to 10 min from a 750 on the 400, depending on your prop size, a 5X5.3 makes the formosa a screamer with the 400 motor