I'm running one single Pulse Lipo 4500mAh on my F450 and two on my F550.. I weighed both the 6600 and two 4500 and found that having a little less than 1/2 a pound (.45LBs) more and 2400mAh more is the way to go.. (I'm not sure if they work that way but I liked the idea..) lol...