I'm not opposed to that, however I wonder if the repeated plugging and unplugging of the reg that goes to the battery balance tap might lead to fatigue in the connector.

On the model I'm working on now (almost finished) I am using a high voltatage input BEC (up to 12S) set to 6V with a back-up battery with reg set to 5.75V, with the same idea in mind... stolen from elsewhere actually. My first time with this set-up but it seems sound.

Tell me now if it ain't!!