Kossel Endstop Mount / Top Frame Brace

Because of the bad torsional strength of my Kossel (15x15 extrusions) I printed some of these frame braces: http://www.thingiverse.com/thing:626279 . Together with my frame braces I reduced the vibration of the printer to the minimum.
You can check the torsional strength of your Kossel if you grab 2 towers and twist them clockwise.