in the inches/mm case... my choice would be, if we can support units, then write the file data as given by the user - use that data as the ultimate source of tr

in the inches/mm case... my choice would be, if we can support units, then write the file data as given by the user - use that data as the ultimate source of truth; use a more efficient/standard representation in the backend and have processes that test that you can re-generate the file from the user as accurately as possible with the backend data. But of course, it depends on the exact case and how much users expect to edit by hand their files.