I have a CMP Hellcat with the same set up, and the elevator likes to move around due to the weak linkage caused by the Y rod. At the very least you will have to connect the elevator halves with a torque rod. If you even use the shafts, I would stiffen them with carbon fiber glued in (6mm fits right inside the tube) and use 4-40 rods on the ends. On top of that you may need some guides to prevent it from flexing. I would also epoxy the rods into the arrow shafts, don't rely on the set screws alone to hold them. Seems like overkill, but this plane will fly very fast with any of the engines in the power range so a tight linkage will be necessary to prevent flutter.