You got extremely lucky with your splits, maybe they were soldered different or something, I don't think it could only be your environment(humidity,temps)
versus mine ! If I were to send you my 6.6, 5.2, and V3 I'm pretty sure you wouldn't get that get a flight time with them. And yes the weight of the 6.6 definitely could factor in the lower flight time but it would be more balanced on sidesaddle's than on the back and I got 39+ minutes with it on the back. So I'm glad that you had luck with the splits but not many people have, how many do you know that I have?