REVgst, I'm not sure I understand your question. You definitley need to batteries in order to isolate them from each other. The ignition battery may carry some noise in it from the ignition unit. By having two batteries, you eliminate the noise of the ignition from entering the receiver throu the battery connection. You can put the two batteries in about the same place in the fuselage to get the CG right. I still try to keep them a few inches apart anyway.