I would use this maxi servo on Mamba Monster Max with its internal BEC.
http://www3.towerhobbies.com/cgi-bin...?&I=LXN610&P=7
Theese are the specs of the servo:
8mA idle and 800mA at zero-load operation
Speed: 0.20 sec. at 60° w/ 8.4V battery.
Output Torque: 16.0 kg-cm (224 oz-in) at 4.8V.
Can I use it without problems or do I need an external BEC?
How many Mah can handle the mamba monster max BEC?