These are the printable parts for the wall mounted spool holders that I use with my MMU2. I don't use any kind of buffer and just depend on the spools to handle the excess when unloaded. In the photo you see the loose loops on the yellow filament that you get when it unloads.

The “terminator” piece is designed to hold a screw-in PTFE tubing connector and it connects to the “bracket” part with a couple of M3 screws.