The post that said the capacity of the battery is questionable is correct. When making battery packs you must know the capacity.
If you're flying a basic 4 or 5 servo aircraft, then a 4.8V 600 mAh battery will be good for 3 or 4 flights.
If your flying an aircraft with 7 or 8 servos then you need more capacity, I have an aircraft with a 2700mAh battery, still with 4.8V as I had 2 retract servos that were rated for 4.8V only.
I use 6.0V packs on most of my other airplanes, some NiCad, some NiMhid. They indeed but out around 7.2V fully charged right off the charger.
Any voltages over 6V I use a regulator. I figure that is a lot cheaper than a new receiver.