Clean up the inside of the horns.
Time to make a template for the tenon. I use 3/16 hardboard and thick CA with accelerator to put this together quick. Start with a large square and cut two pieces the same length and 1/3 the width of the larger square. Mark a centerline. Then measure out from center and put marks for the outside edges of the neck tenon. These are just guides to make sure the neck tenon is centered on the template. Spray the accelerator on the large plate, put the CA on the smaller piece and glue it right on the line, clamp it and let it dry. After it is dry set the tenon tight against the edge and repeat the process for the other side. Remove the tenon quickly or it will get stuck permanent. After all is dry glue a piece to act as the end of the route. Drill out the center and clean up with a flush cut router.
Mark the neck placement. Attach the template and rough in the pocket with a forstner.
Test fit the neck.
Stopping here until I get parts.