Prusa Mini Spool Holder - sits on Z-Axis

This is a spoolholder that sits on top of the Mini's z-axis. Print the part using supports at 0.2mm layer height. You will need to disassemble one of your original Prusa Mini spool holders. This print replaces one side of your spoolholder. See photos. I used the original Prusa Mini spoolholder stl file, so it will match up exactly with your current parts. It works great. I've printed one of these for all three of my Minis. I have two suggestions to get the most out of the holder:

1. It's stable with a new 1kg spool of filament, but to improve its stability you should print the mini base. See the photo above to see my setup. 
2. If you have very little filament left on a spool, you may have issues with some filaments not rolling smoothly on the bearings and the spool may get pulled off the back of the holder. To prevent this, orientate the spool so that it spins towards you, standing in front of the printer (imagine the spool rolling towards you). You will feed the filament to the filament sensor from the underside of the spool. This helps to keep the force on all of the bearings equal, so it's less likely to get pulled off the back of the printer. Again, I've only experienced this with spools that have very little filament left. This is simply a preventative measure. See the photos above and you'll notice how I have the filament fed. The orange filament is NOT fed this way because it's a new roll so I knew it wasn't in danger of being pulled off the holder. But the blue/black filament roll in the photos is rotated 180 degrees, so the filament is pulled from bottom of the roll instead of the top. 

Added some more description and recommendations.