Check the output of the BEC, voltage needs to be compatable, usually just isnt an issue.
Also if using hi torque servos, you'll need a 3A or above BEC. I allways use a esc with a 3A BEC when the plane has 4 or more 9g servos, just to be safe.
Some servos are VERY sensitive to when to BEC voltage drops a bit low(from drawing too much current from the BEC), and could start to go crazy