Now an enquiry about Quenya.
Are there any examples of Tolkien actually using the 'Last Declinable Word' rule ever in any text proper, not a grammatical sample sentence? I found none; and even, without much heavy search, at least two explicit contradictions, both in late Markirya: rámainen elvië 'on star-like wings' and ondolissë mornië 'on black rocks' instead of rather expected rámar elveäinen or ondoli morneässen. (Of course these patterns are copied from the first Markirya.) How does that fit with, for example, PE21:77's But Sinda Eldo, a Grey Elf's, Sindar Eldaron, Grey Elves', or (abnormally) Eldar Sindaron? Can we resolve that, for example, proposing that cases (genitive, accusative, dative) are postposed but adverbials (three locatives, instrumental etc.) are not?