10 servos, most of which are idling for the vast majority of the flight. My Ki-61 has about the same number of servos (actually more because I have two for a bomb drop and a servo actuated canopy) and it only uses about 250 mah per flight on a 2000 mah 6V pack. No doubt, a 6V battery will discharge a bit faster than a 4.8V, so you need some extra when using 5 cells but I am certain I will get 5 or 6 flights easy with a 2000mah 6V battery with the servos I am using (two digitals, the rest standard). I think it would be a waste to use digitals on the flaps, throttle, and retract servos. The most you need on this plane would be 4. I would never push someone away from being "safe" though, so if you think you need more capacity, use it.

As for using 6V, I have never had a servo that had a problem with it, even standards like a Futaba S3004. I have seen cases where other people have had some "chatter." One advantage of a 6V pack is that you get to use the entire rated capacity. Since the low voltage level is still plenty for the reciever the battery has to be very low to cause a problem. A 4.8V battery cannot use it's entire capaciity because the low end of the voltage range is too low to operate the receiver safely.