Parametric Spool Roller

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.