1) Reinforce the area where each rear stab half is glued into, as mentioned above.
2) Use a single internal joiner wire for the elevator and either a stiff carbon fiber rod going to it or a servo mounted in the tail close to the elevator.
3) If I use a carbon fiber rod with the elevator servo mounted up front in the servo tray, then I would mount the servo longitudinally (parallel to the fuse) to reduce servo rocking as the elevator is being deflected.
4) If I don't use a carbon rod for the elevator, then I could use a metal pushrod inside a nylon tube and anchor the tube to wooden cross braces placed across several formers inside the fuse.