you have to tram the head to the column in both directions. scraping the back of the spindle block/slide block is far better than shimming...if you have the equipment! shim/scrape for the Y deviations, gently tap with rubber mallet for the X with the clamp bolts slightly loosened. if you could handle it... insert locating pins when satisfied its perfecto.... then its easy to reassemble after the occasional maintenance or modification, and "shouldnt" lose location if it happens to crash... unless youre going to try replacing that solid join with a rotating section... sort of pointless on an X2 unless you have a feather spindle.
really, the whole machine needs a good scrape. gibs particularly need attention, they flop, they lift in the slot and bear on the wrong part, yarda yarda. the adjustor screws really need to be pointed.
then you have to tram the column/spindle to be square with the bed. once again...scrapings best in the Y axis. finding a shim THIN enough to get the column squared up in the Y is a nightmare... very narrow face in that axis means the slightest change makes a huge difference! and you dont have much width on the bed in that direction to get a good reading. 0.01 across 100mm is shocking compared to the 0.01 you can very easily get across the 600mm of the bed...
yesh, i use metric.
i know i personally preferred scraping each part to be square with a surface plate rather than the fiddly tediousness of inserting shims, checking, rechecking, triple checking... each to their own. there was some fiddly tediousness in making the plate itself! but now its there, when i need one
as far as i can tell, it doesnt matter a hoot if the face of the column isnt parallel to the bed. when looking down the Z. why should it? as long as everything else is square it works.
with so much stuff on hand, one spends more time locating it rather than using it.