Printrbot Original Build Platform

This is my version of the build platform intended for the original Printrbot with the 6" x 6" build area. It's designed after beardface's 8" x 8" build area platform (http://www.thingiverse.com/thing:17717), but the hole spacing is designed to match Brook Drumm's original Printrbot (http://www.thingiverse.com/thing:16990).