RE: 4.8 to 6 volts
There was a post here a couple of months ago about changing from 4.8 to 6.0V. It said that it made the servos jitter. I put 6.0V in my sailboat and the rudder fluttered until it got in the water. I've used 6.0V in an airplane and had no problems with the servos. One did jitter and I sent it back to the factory, it was brand new, and the fault was with the servo itself not the extra voltage. Changing shouldn't be a problem. Just check it out before you fly.