RE: rx battery
The only manufacturer I've seen that is nervous about putting 7 volts through their receiver is Futaba who recommends not to use A123 packs, and there are plenty of guys who have done it anyway with no problems. The manufacturers know how much voltage our packs actually put out. A 4.8v pack is rarely actually 4.8 volts in actual use; it's usually a bit higher because that's how NiCd/Nimh batteries work. The manufacturers know we will put 6v packs on our planes that will be at 7 volts hot off the charger, so they design their systems to work with the actual voltages the packs will put out in normal use.