Printrbot Simple Adjustable Spool Stand / Coaster

This is a modified version of Ramai's "Spool holder, Adjustable, from PB design." Requires 4 skateboard bearings.

If you are not limited to a 4x4 bed, then you may consider his design instead.
http://www.thingiverse.com/thing:178862

I wanted to be able to print this coaster on a smaller printer. Mine is a Printrbot Simple and it only prints 4x4x4. I'm sure the design can be improved but I made these modifications in under 2 hours.

I put screw holes in the fins and the coaster so you c