>Incidentally, does anyone know why the accents are written over the
>second element of a diphthong rather than the stressed component?
Writing it over the second element indicates that we have a diphthong
(digraph, eg written <ou> and >ei>). You can sometime see the accent on
the first element, which is a clue that the two vowels are to be read
separately - it functions as the equivalent of diaeresis on the second
vowel. I can't think off hand of good examples, but I know you can find the
form Aide:s with breathing and accent on the first vowel (or before, if
capitalised) which means the word is trisyllabic.
Peter