When you mount the scales, make sure to mount them parallel & plumb - so that scales are not stressed as you move the table in X or Y.
Sometimes you can let one of the end of the scales float - this way the scales can "self-adjust" .
If I were to add a DRO to my mill _these days_, I'd seriously consider going with an Ebay 2 or 3-axis glass scale DRO kit. I had my share of issues with flaky 18" chinese scales. Loosing positioning during a job and having to re-establish 0 can be very annoying
