Printrbot Plus V2.1 X-axis Spreader

I noticed that my PrintrBot Plus V2.1 would have problems printing very tall objects - towards the top of the Z axis, the small amount of wobble of the z-axis guides is pronounced and leads to the sides being slightly closer together. This causes the belt tension for the X axis to go slack, even though it is tight at the bottom of the Z axis.

I solved this by adding a tensioner across the guide bars using a 12" length of 1/4-20 rod, two couplers, and printed brackets. Enjoy!