The elevator halves are typically connected by either a regular Y connector or a servo reversing Y.
Since I am cheap
, I use a regular Y. Just physically reverse one of the servos - have the output shaft of one closer to the rear of the plane and the other closer to the front of the plane. Another option is to use one Futaba and one HiTec servo (they rotate in opposite directions).
FWIW - I never heard of an "ailevator" function. Are you sure you don't mean ELEVON ? Elevon is when you have something like a delta or a flying wing (Zagi) and the elevator has to also work as ailerons.