Small "improvements" on the Printrbot Y bar ends.
Allow 3 of the corners of the build platform to be adjusted while limiting one side's compliance in the X dimension.
I have a set of small springs, and knobs to adjust the height of the bed. The nuts are: http://www.mcmaster.com/nav/enter.asp?partnum=93886A110
The springs were something I had lying around... I hate it when people say that because now what are you supposed to do? Hopefully for you the reader, either you don't care and your just reading this for charity, or you or someone else cares enough to find something and then post it or make a derivative.
Keep the bar end that has the adjustable stop. This will set the height of the bed (you can adjust the zstop to this height. Use the tabbed end at the other end of that Y Bar. This needs a spring as pictured. Your build platform will require a small hole to attach. The long tab will limit the build platform's compliance in the X direction
The smaller Y bar ends may be used on the opposite bar as pictured. They're designed to be compliant in X, though you may have to drill out the holes a bit. You'll notice mine are at a bit of an angle because My y bars are wider than intended in the original Printrbot design. Tightening the original parts would have broken the plastic and/or caused the Y bar bearings to be unessecarily loaded. (It was my fault, I didn't drill out the holes for my x bars before installing, so the carriage is too large.