I am building the Big OX and the two beams for the x-axis meet perfectly on both ends but there is a small gap (about 1mm) in the middle. I can easily squeeze the two together and then the gantry runs smooth... but otherwise scraps a bit around mid point. I already tried loosening the screws and re-tightening with them clamped together but that didn't help. >> I just finished the x gantry and really don't want to take it apart to try flipping the beam... but if that's the way... Can I throw a small bolt & screw in the middle to keep them together? Thanks!!