I made this spool holder for my MK3S because second printer is located above it. Its mandatory to choose correct thread orientation otherwise, shaft will loose during printing. On the pictures, you can see  left hand tapped thread what eliminated this momentum. In case of using this mount on opposite site you will need to choose right thread.

I had print my from PLA because of reducing my storage space. I had use 5 perimeters for strength increase. But I would recommend to use some more technical and stronger material as PETG, ASA, others.