2020 filament spool holder with 608 bearings

This is a remix of http://www.thingiverse.com/thing:172484

Modified to mount to 2020 using a single 5mm t-slot nut. I also added a space for the head of an 8mm bolt to recess into the mounting plate of the holder so the bearings can sit nearly flush with the mounting plate.

To prevent this from breaking the mounting plate in half like my first one did, I added two holes where wood screws can be screwed in from the bottom to give it strength. The first one I printed broke, because it