I talked to Sadnam just in time
I have kept away the 4.8v Sanyo Rx Battery I got with my Radio along with Servo Tester for all calibration/test purpose.
Use of BEC along with 2S lipos are good option to NiMH but there is always a chance of over discharging the LiPo below 6 volts before you actually face Rx Brown/Black outs