PTFE Tube Adapter for Printrbot Aluminum Extruder

I have a printrbot simple (2013 V1 heavily modified) that's still chugging along. The one
problem that has bugged me about this style of printer is that the cantelever design
causes horizontal lines along vertical walls when the Y-axis pulls against
a filament spool.

For the longest time I thought this was related to an issue with the acme rod being off
center, but eventually realized that my acme rod is properly centered and the problem
was really just spool drag along the Y-axi