Bend a piece of 3/32" or 1/8" (or larger if it is a BIG plane ) music wire to connect the 2 elevator halves together.
Next get some 1/16" (or heavier depending on the model size ) sheet brass.
Mark the outline of the horn on the brass, BUT DO NOT CUT OUT YET.
Now drill a hole for the wire that connects the elvator halves and a 1/16" hole for a METAL PIN clevis.
Now you can cut the horn out.

Clean the horn up and emory/sand the center section of the elevator connecting wire.

Slide the horn on the wire.

BLOCK THE WIRE IN A LEVEL POSITION and adjust the horn for the angle you want/need.

Solder with a SILVER SOLDER. I can highly recommend Stay-Brite solder. Their flux is a liquid and excellent.
Use at least a 60 watt soldering iron to heat the center of music wire and solder.
After everything has cooled, clean the solder joint and TEST the horn to be sure you got a solid solder connection.

I like and use Sullivan clevis because of the locking clip.

Install the clevis to the pushrod and install. Be sure that you either solder the clevis to the push rod or use a
nut to jam the clevis so it will not move.

Remember, you will ONLY BE ABLE TO ADJUST THIS FROM THE SERVO END, so make sure everything is correct
before sealing the fuselage (and access ) up.