Trying to get the adjustable rails set in the correct location was bothersome so I modified it to use screws and nuts on the outside of the rails and a press-in piece on the inside to lock the base pieces in the correct width for a standard 1kg spool. This has been working well for me so I thought I would share it.
I added an exploded assembly drawing to show what is needed and how it goes together. I used some off-the-shelf bumpers for non slip feet on the bottom.
The author remixed this model.