Here's my take on keeping the x, something I had no issue with in the 12 years that I used my Rong Fu. It's a simple trick called a datum. Here's what you do- pick a spot on your table, vise, or whatever can be traversed under the spindle. Take a spotting drill and punch a dimple in that spot. Say it's the frontmost right hand corner of the jaw closest to the operator's position. Before changing a tool, traverse the datum (dimple) to align with the spindle. A pointy tool in the spindle helps. So you're aligned to that spot, your DRO says what it says for that datum. Now raise your head and change your tool. Lower the quill to point the tool into the dimple at the new head height. Tighten the head. Now you're aligned, and you pick up where you left off with your DRO.
Does it make sense why I grumble over some of the complicated fixtures for maintaining zero (play, backlash, and all)? I've seen some nice ones, we have one amazing example here, but it simply isn't necessary. You'll get better alignment from a datum.