I've got a 33% FC Extra 330LX and I did not use them on the ailerons ... have had no issues with two 8411's in each wing. Very consistent (and normal) battery drain.

My rudder has 3 ganged 8411's in an SWB tray ... one going into one receiver straight and two going into the other receiver through a matchbox. The single servo is the "master" and I "match" the other two to it using the matchbox. Very easy to setup and I have redundancy on rudder since they go to two separate receivers.

Good luck with yours ...

Jamie