>When sheva under a guttural consonant becomes vocalised, the
>vocalisation is always a composite sheva
Though this doesn't affect your original argument, it's worth pointing
out for the sake of accuracy that when a shva under a gutteral
consonant becomes vocalized, sometimes it will NOT be composite. If
the would-be composite ("chataf") shva falls before another shva, it
then turns into a full vowel. For example, YA'AV'RU (they will pass)
gets a full vowel under the AYIN.