Update: 13-02-12: Updated the scad file, with guards, and stl with larger radii under where the bearing should sit. I was having an issue with clearance while printing so I added 1mm of space.
Update 13-02-10: Updated the scad file with some spool guards on the outside of the frame. Should help the spool from falling off. I may need to add them on the inside as well but I am hoping that since the roller is one piece the outsides will be enough.

Derived from thing:22579 as there were a couple issues with scaling the spool. I tried to make sure the base radii were flush (or as flush as possible in the case of the long side cut outs) with all spool sizes to minimize material and eliminate overhangs. Also tried to give a suitable variable value to the length of it to keep the spool stable.

I've printed versions with as little as 15% infil (all have been PLA) and they work fine. The file should be parametric but I haven't tested it for a boat load of different spool sizes or bearings.
Currently I have 608 bearings so I re-designed it for them but it should work with other types. I use mine with some extra threaded rod I have left over, or you can use 8mm bolts, smooth rod, bundles of filament, etc.
I'm still looking to add in a design to help guard the spool from coming off the sides as it gets lighter.
The included .stl is for my spool at 204mm in diameter and 72.5mm wide (including the walls).