Phonetic Mapping of the Hiragana System Used in the Okinawan Omoro Sōshi


The classical Okinawan poetry collection the _Omoro Sōshi_ is written (mostly)
in Hiragana, but the phonetic mapping of the characters to sounds seems to be
different to their standard mapping.

For example, the title "おもろそうし" was presumably (according to the [Okinawan-
English
Wordbook](https://books.google.com.au/books?id=8guTfpBKm5kC&source=gbs_navlinks_s))
pronounced more like /u.mu.ɾu u.soː.ɕi/.

Short /o/ and /e/ in standard Japanese seem have been shifted to /u/ and /i/
in Okinawan respectively, and moreover, Okinawan phonology seems to
distinguish between /ɸ/ and /h/, and seems to feature glottalized vowels,
approximants, and nasal consonants, all of which are not distinguished
according to the standard mapping of the hiragana.

So my question is, how did the hiragana orthography used in the _Omoro Sōshi_
correspond to the pronunciation of the poems? And did it adequately map the
phonetic inventory of the language, or was it
[defective](https://en.wikipedia.org/wiki/Defective_script) in some regards?

