UPDATE_OCTOBER_2019- SOMEONE ASKED FOR A FRENCH CLEAT DESIGN. I HAVE ADDED THAT.
After being tired of looking for a good way to use the Spool Rewinder on my MMU2s Prusa machine I finally made my own. I didn't want a big "BUFFER" behind my printer and 5 spools on my limited desk space. This allow you to use the rewinder spools https://www.thingiverse.com/thing:3338467 and mount it to your wall behind the printer. This is two parts... One is a mounting rail, and then the spool holder itself slides easily onto the rail, and then is secured with two 3mm allen head screws... This works great. There is a spot to accept the MMU PTFE tubes from the MMU2s, and also a small tube to guide from the spool.
I printed with 5 shells... 50% infill GRID infill. I used some supports on the back.