Two threaded-rod cross-bars through the top-most frame-vertices aren't really necessary for mendel's structural integrity. Further, the z-bar-top-clamp parts are larger than necessary. This is a modified frame vertex that's smaller than the standard one, requires only one threaded-rod cross-bar, and uses whowhatsis's pinch block y bar clamp ( http://www.thingiverse.com/thing:3843 ) instead of the z-bar-top-clamp for additional printed part savings.