RE: Servo Reverser ?
A reverser is needed to have both halves move the same, with the servos mounted with the axis of rotation aligned with the elevators. (usual back of the fuselage installation.)
A reverser isn't needed if the servos can be mounted with the axis of rotation 90 degrees different from the elevators.
Then, using opposite sides for the horns will work. (mounted forward in the cabin, typically.)