I will be changing my FrSky Q X7 to LiPo batteries when it arrives. While I use three cell LiPos in my aircraft, I see there is the option of using 2S or 3S LiPos in the Q X7. There is no information given about the regulator the Q X7 uses to bring the battery voltage to the Q X7 voltage. If it is a linear regulator there is almost no duration advantage in having the third cell. If it is a switching regulator ( with its current boosting ) the third cell will provide a 50% increase in duration over two cells. Sorry this is more technical than most flyers need but the open source nature of the Q X7 should include information on the hardware as it relates to this upgrade.