DIY Schroeder Tonearm???

It's not easy to mill the wood and then glue the pieces together to make it even. Of course, anything is possible if you have access to precise machines. The hole should be as small as possible. If it were to be e.g. 3 mm, it would be 1.5 mm on each side, and this is not easy to do in the case of wood. For me, it was easier to drill, so I have never tried milling and gluing, so I can't help because I don't have experience.