Thanks guys, lots of things I obviously didn't consider - or improperly stated - in my 1st post. But I'm still not comfortable with (intentionally or not) exceeding Mmo, even if I can "rely" on this safety margin. U could actually claim the "safety margin" as an excuse to exceed any other parameter as well (eg MZFW, V1, "g" tolerance, C of G, flap extension/retraction, etc). These speed - or weight - limits have been established for a good reason (same story on the road, actually) & I'm not the one who'll put them to test. Better to have the law on your side.
MF