It’s finally done. After countless versions, broken parts, failures over and over again, here’s the final design or to be more exact: the two final designs.
I’ve come to hating spool holders in the process to be honest. 
(This is a follow-up to https://plus.google.com/116938148382581356502/posts/7ExGSVFTW6n)
http://www.thingiverse.com/thing:1929562