So I Just got done testing this mod, and I wanted to let you know my results. I know that there is a lot of controversy over whether or not these actually work. In sport mode the batteries add about 4.3 minutes of flight time, while in regular flying the batteries add about 8.2 minutes of flight time even with the extra weight. It's not a huge difference but it can come in handy. I also like the way that the Mavic flys with the extra weight, it feels more stable. The mod I constructed above weighs around 176 grams in total. After about 2 hours of testing I have experienced no problems. I did a lot of research before testing this in the field and found that the extra power on the Mavics battery cells shouldn't affect it. My guess on how this works is that the LiPo batteries charge the Mavics smart battery while it is flying, as the remote doesn't read any extra mAh or volts, another reason I have for this theory is that the LiPo's can be used for three flights before they should be charged again. I am happy to answer any questions.