I would be careful about running Futaba servo's on 6 volts, some have reported that they don't like the higher voltage and have fried theirs. If you want to run Futaba's get a voltage regulator and run them at 5.5 volts and they should be fine. Remember that a freshly charged 6 volt pack can put out over 7 volts. Hitec and JR seem to be fine with running at the higher voltages though.