Oh what a chatterbox I am.
Anyway, the document I have is an extract from NASA STD-3000 which is more general (and may be aviation inspired - I haven't read it). Unfortunately, MSIS as it is called, is only available from NTIS for money (140USD) so I am disinclined to check.
My (new) reading of FAR 25.777 is that no HF standard is used. Flight deck designers therefore have plenty of scope to make mistakes. The certification process probably involves two people of indeterminate age or physical type, who just happen to be minimum and maximum height, twiddling the controls and peering at the instruments/displays. Sorry, but that is how I would interpret a requirements document written the way FAR 25.777 is.
Stevenson
------------------
Mare Crisium Srl