[MetalMan]

You could also splice a switch onto the red receiver wire as it is required for the BEC to supply power to the receiver. This switch on the red wire could serve a dual purpose; if you ever use a UBEC you could have the switch turned off without needing to take out the red receiver wire.

Just make sure that if you do use a switch that you still unplug the batteries. The 9920's circuitry will still draw a small current even when it's not receiving a signal.