Hey John @jnordyke, hey Bill,
if you now proceed the way I suggested (with one ruler attached to both hollow shafts at the right end of X, and one ruler the same way attached at the left end of X, both prolongating the alignment of the shafts one over the other towards ceiling, and thereby exaggerating (=making more visible) the tilt of the two shafts at each end) and you use the tramming bolts to align them so that the tilt is identical both at the left end of X and at the right end of X travel, then you can repeat your measuring perpendicularity to the table with your 15 inch measuring arm in the collet, once at left and and once at right end of X travel. If then, you still have a different tilt on left side and on right side referencing to table, then you have proven that your table is twisted (i.e. is not coplanar, i.e. has one foot higher than the others).