The Prusa MMU buffer has never really struck me as being very practical. So I decided to design my own. After several iterations I came up with the mini buffer. Just connect it to the end of your MMU PTFE tube (using a bowden connector) and the filament just unspools into a loop. When the filament is required again it simple spools back in. No need for auto rewinding spool holders etc.
Optionally you can use 2 lengths of PTFE tubing if you feel that the filament is not feeding correctly without it.
No need to for any supports. Simply print with whatever settings you feel are best.
Please give me some feedback and I will try to improve the design as you feel fit.