It’s also worth noting that while the OCH should be rounded up to the nearest 10’, those pesky surveyors have gotten more accurate!
When we add 350’ (for example) to our 13’ field elevation we get a minima of 363’. Should we just revert to using QFE to regain the lost 7’ after the second rounding? And of greater magnitude, what about the altimeter setting? We could be missing almost 30’ for a millibar/hectopascal that’s about to change! If we switch to inches Hg, it would be a maximum of 10’.
Maybe some are missing the big picture? The procedures devised cannot hope to be absolutely precise, just follow your Ops Manual procedure. And if you’re writing your own ask the lawyers…
Good luck.