Schummie, a 2000 mah battery would be plenty. I use NiMh cells and have had excellent results.

Since you are using a 9 channel PCM receiver I assume you have a Futaba 9C or more. I will use y-cords on some of the servos to provide what I need. I plan to use normal channels for Elevator, Rudder, Throttle, and retracts. I will use channels 1 and 6 for the two aileron servos. I will Y-cord the flaps together and also use a Y cord on the air brakes and plug them into seperate channels. I will then program them to follow each other on the variable knob I always use for flaps. This will allow for seperate adjustment if I need more or less brakes/flaps. That makes 8 channels. On a 9C if I remember right channel 9 is not mixable, and in my case I will not use it.