RE: Charge to 4.1v/cell
Another way to look at it: A typical flight starts at 4.2V per cell and ends around 3.8V per cell, give or take for wind, flight time and/or traffic avoidance. The difference there is 0.4V of usable eMF in the battery, the potential energy that our motors convert to the kinetic energy that moves the airplane. Now, if I start a flight at 4.1V, I only have 0.3V of eMF to apply to the motor: That's 1/4 less eMF than I had before when starting at 4.2V. It stands to reason that flight time will decrease given the same flight profile; and I risk asking for too much from the cells if I attempt the same flight, potentially stressing them on the low side. With just a precious few minutes of flight time on a full charge to 4.2V, I really don't see much value in departing with less eMF than possible, as a matter of choice. But that's just me: I like to have a full tank of gas at the start of each flight. Cheers!