Guide for Spool holder
I printed this one (http://www.thingiverse.com/thing:93652) as I was looking for a minimalist spool holder I could use with spools of different sizes. The only backdraw of this holder was the spool was falling in the gap between the bearing and the holder. I could have modified the original STL, but it was faster to draw that and print it.
You just have to put it inside, the final gap is 4,4mm.