RE: 4.8V versus 6V for receiver battery?
Yes, it is true that the 6.0 volt battery will give you a faster servo response time as well as more torque. I use a 6.0v battery on my UltraStick because I wanted a faster servo.. It is also true that the 6.0 volt battery will run to depletion faster than a 4.8 assuming they are both the same capacity (mAh).. The rule of thumb that I've heard is to get a 6.0v battery that is has 25 percent more capacity than what you think you would need in a 4.8v.. This is a ballpark number, but works most of the time.. I've been happy with a 1200mAh 6.0v battery in my stick running 7 servos.. All depends on what type of flying you are going to be doing. If its just a trainer, you want the servos to be slow, but if you want to "amp" the up a bit give the 6.0 a try!
John.