Don't despair, Andrew! We listen, even if we
don't respond. I didn't, because I leave that for people who know more
than I do. And it seemed already clear from your email, that you were in
touch with the same stuff as I am.
H4 does seem to be an invention purely to explain
the unexpected absence of H- in some Hittite words. It has not won wide
acceptance, as far as I know, because inventing a PIE phoneme just for one
languae is inefficient.
Other threads I'll leave for other
people.
Peter