RE: A123 as receiver pack - no fly voltage?
Psk 560,
I only charged mine to 6.7 volts. I was nervous about unregulated on 7.2 volts because they don't come off the voltage like my Nimh's did. (the nimh's were down to under 6.5 volts in the first flight the A123's took two flights to go from 6.7 to 6.66)
For your question #2 I do'n't know the answer.
I tested with a 250 mAh load and typically got a .10 volt drop.
I hope this helps.
Richard