Lipo Receiver Batteries a good idea?

[BrianG]

2s lipo is 8.4v fresh off the charger, and 7.4v nominal. If your receiver and servos can handle this voltage (and the added current generated by this higher voltage), then go with it. As you said, you'd need an LVC, or some other way to monitor the voltage (LVA, telemetry, etc).

5 NiMH cells is around 7v fresh off the charger (~1.4v/cell), but drops pretty quick to the nominal 6v value after running and when loaded heavily (from a high power steering servo). Most receivers/servos handle this ok.

Personally 2s lipo is too high. If anything, 2s LiFe cells would be better. A 2s pack with those cells would be 7.2v fresh off the charger (3.6v/cell), which is much closer to NiMHs fresh off the charger, and 6.6v nominal (3.3v/cell).