The recommended Mark Medium is Large enough to rest headphones on. The base and head/neck are meant to be printed seperately.
Members get access to my premium files and authorization to use the prints commercially.
I recommend laying the skull back so the neck is parallel with the build plate and then using tree supports. 1.2mm wall thickness and 10% infill.
If you are intending to use for a headphone holder, please take measurements and scale accordingly.