If you look at my picture, notice that the red wire was removed from the servo connector, this is how you remove the wire:
Then simply use a pin and insert it into the exposed female red wire you just removed, and plug that wire into the #2 cell of your balance port on the 4S battery... use your voltmeter to check that the #2 cell reads 8.4V, that is the hole you want to plug the red wire into, this will bypass the BEC.
Only do this if your Rx is rated to handle 8.4V otherwise you'll need to get a UBEC that I linked above.