I have an internal BEC on Mamba X ESC from 5.5 to 8v. I have not yet installed a Castle BEC 10 amp peak (6S 25.2V max in. 4.8V-9V OUT) external BEC. I'm using a Savox SC 1258TG servo. Do I need to install the external BEC? What voltage settings should I set to the internal one on the Mamba?