The B-side of the album Poems and Songs of Middle Earth begins with a
reading of the Sindarin poem A Elbereth Gilthoniel by J.R.R. Tolkien
himself, and in this recording, as best I can tell, he always pronounces
short i (i.e. ⟨i⟩, not ⟨í⟩ or ⟨î⟩) as /ɪ/ rather than /i/, regardless of
stress; for instance, the word “silivren” has the same i-sound twice (it
is not “silívren”). I believe this means that we should use the phoneme
[[I]], not [[i]], for ⟨i⟩ (in both Quenya and Sindarin).