One way to do it. At the receiver all the black and all the red wires supply power to the servos with the yellow wires carrying positioning. So break all the red (positive) lines from the servos. The end of the lines that connect to the servos are now wired to a switch harness, tape the other ends off. If you are going to use two battery packs just use two switch harnesses in parallel. The black wire from the switch harness is spliced into the black wire going to the receiver (it's the common).

Wire the receiver normally with the 1100 mA battery pack and you are done.

John