RE: TX question
My fellow Virginian,
You can use any size mah battery you'd like. 1200mah battery would be no problem. Find one at your LHS or online estore and purchase it with the Futaba connector if it's not a Futaba brand battery. You are correct on the "J" connector. The old radios used "G" connectors. Your R127DF receivers are still current today. Futaba still makes this receiver. Other than putting new batteries in the TX's and new flight pack batteries you are good to go! Of course you can still get a new computer TX to use with your current receivers and servos. Just stick with Futaba TXs though. We don't need to go into the whole positive, negitive shift thing!
Later...
Scott!