Do you think the RX will handle 7.2 volts ? Actually a fully charged 2C lipo has a bit over 8 volts.
When dealing with high voltage servos I think you should use 2 batteries: a 7.4V lipo regulated to 6V (or the usual 4.8 / 6 NiMH) for RX and another 2C lipo (aprox 7.4 - 8v) for the high voltage servos.
Servo city sells a device that will help you to connect the + /- wires to a second battery and the signal wire to the RX. Or you can build your own.

I had the link but lost it .... I will try to look for it later on.



George