I have always run on 6V ... nothing has happened to my JR/Futaba/Airtronics. Please remember that the radios were made for people who might run normal batteries. That would mean 6V for 4 cells. I asked JR about the rumours of their RX burning if we use 6V, they said its nonsense. For me 6V will give me some added peace of mind that the voltage drop will not be that fast when I run standard servos (not sure if this is true at all!!!). For me its not about the speed and torque as I am flying 40 and 60 sized planes only. I use the 5 cell NiMH cells used by RC cars for their RX.