RE: What is the cutoff point for lipo's
The low voltage "resting point" for lipos is 3.5-3.7 volts per cell. For power systems there's no useable capacity below 3.5 volts , but since you are using in radio app with low current then there will be some useable capacity below 3.5 volts/cell. I'm not saying that you should use this extra capacity.