I really like the spool holder design from filamentry but the only problem I have is that sometimes the spool holders collapse.

Thats why I designed this version with one or two bars between two holders.

You need four TUSH_Bee_side  and one TUSH_Bee_bar. 
Or just print the TUSH_Bee.stl

You also need 4 608 bearings. They will snug fit on the side piece   

If you prefer an more rigid holder,  choose the TUSH_Bee_2bar.stl