Phonemic vocalic length in PU/PFU (was Re: Questions aboutHungarian)

Paul Bennett wrote:
> Maybe the process of (Intervocalic Voiced) Stop -> Fricative -> Glide ->
> Zero ?
>
> Maybe (Voiced) Aspirated -> Breathy -> Schwa glide -> Schwa assimilation ?
>
> Both of those are plausible to me (after only a second or five thinking
> about it), although I cannot speak for the actual processes involved in
> PU/PFU.
>
> Paul
Monophthongalization of diphthongs is another possible source.  In
Japanese, for example, there was a sound change /eu/ -> /jo:/
(presumably thru an intermediate /jou/), and /iu/ -> /ju:/.  Loss of
intervocalic /k/ was another source, e.g., the suffix /Siki/ -> /Si:/.
Loss of coda consonants can be a source as well, e.g., Latin had changes
like /ans/ -> /a:s/.

However, I also know nothing about PU myself, either.