Prusa i3 MMU Retraction Management / Hanging Spool Holder

Update: 11/21/2018: I ran into some PTFE that wouldn't fit into the guide arms, it was thicker than what I was using before, so I have added two arms that are slightly larger diameter to allow for this.

Update: 11/15/2018: So I have moved on from the awesome universal spool with the screw in sides. It was just a bit much especially when I needed to change out a filament. So I designed my own hanging spool (inspired by many others available on Thingiverse). Anyhow, the hanging spool has a