RE: Help calculating remaining flight time with LiPo's
whatever charger you are using should stop charging @ 4.2v, that's correct. as for the drop dead voltage, that seems to be a hot topic. i've gone with 3v, which seems to have the majority's vote. i think i've also seen posts stating that mfg's recommend no less than 3v, also.
p.s. that's 3v under load. when you take it off the plane and check the voltage, it's gonna be higher.