Check out this interesting discussion from a while ago about doing exactly that.
I wonder if this “worst case” belt stretch is relevant though, since most (all?) people doing high-precision parts will use a separate (and light) finishing pass to get to final dimensions, and very little force = very little stretch then?.
Some people seem to achieve 0.0002" tolerances on parts with a Shapeoko with regular belts.
This being said, these comments comes from the guy who spent an unreasonable amount of time mapping the belt stretch on his machine, to finally realize that it’s way simpler to just run a job, measure offsets to target dimensions, adjust stock to leave/offsets in the design, rerun, done. It was a fun journey though.