The home strait (sic)

The book is nearly done (that is, completed in its first draft – what to do with it thereafter is TBD [To Be Dithered over].)

Here is the latest tranche (not as trencher-like as previous instalments; less to get your teeth into) because the vowel pair in question isn't so prolific.

Vowel sounds represented by the spelling 'UO'

A large proportion  of words spelt with the vowel pair '-uo-' (57½%, to give a percentage that on such a small sample size is not particularly significant) are excluded along with other words spelt with the ending '-ous' (as explained here [the link doesn't work here]), specifically '-uous' . The Macmillan English Dictionary provides two transcriptions of these 35, assigned apparently randomly: /juə/ and /jʊə/.
This apparent discrepancy suggests the hypothesis that the prefix in some way 'causes' a supposed vowel change.The words discontinuous and inconspicuous have /u/, and continuous and conspicuous have /U/, which supports this hypothesis. However both ingenuous and disingenuous have /ʊ/, which suggests that the beginnings of a seeming pattern are illusory.
Another possibility is that a stressed vowel in the preceding syllable goes with /ʊ/. This rationale works for  both continuous and conspicuous, but not for ingenuous, which has /u/. Perhaps the apparent distinction is just accidental⁽¹⁾.

...

UO Notes

1. Words spelt '-uous'
   The apparent randomness might be explained in this way: at first two researchers were working on these words (words spelt with an initial a-f were shared equally between /juə/ (2 a-s. 3 d-s, 1 f-) and /jʊə/ (1 a-, 4 c-s, 1 e-) . One oddity resulting from this division of work was that discontinuous is transcribed one way and continuous another. For the 17 words with initials from i-to-  the researcher with a preference for /juə/ was working alone. For the last 6 words, tu-v the researcher with a preference for /jʊə/ was working alone.
   But my use of was and were in this tale of backroom staff management  is entirely speculative; the distinctive transcriptions may have fallen either way completely by chance. In any case, the student may safely ignore the distinction.
2. fluorescent
   Macmillan English Dictionary uses the transcription /flɔ:'resənt/, but the audio sample has a similar diphthong to the one in the word transcribed as /'flʊərəʊkɑ:bən/. Meanwhile, as further evidence of the variable pronunciation of this vowel sound, the words fluoride and fluorine are transcribed with the diphthong /ʊə/ but have an audio sample with a monophthong that is not unlike /ɔ:/.
3. duodenum
   The Macmillan English Dictionary gives the transcription /dju:əʊ'di:nəm/, but the audio sample gives both unstressed vowels as /ə/. Again, the student may safely ignore the distinction. Full enunciation of the diphthong is reserved for very careful speech.

Ho hum. Back to the grindstone.

b

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 Mammon (When Vowels Get Together V4.1: Collection of Kindle word-lists grouping different pronunciations of vowel-pairs – AA-AU, EA-EU,   IA-IU, OA-OU, and – new for V4.1 – UA-UE.  If you buy it, contact  @WVGTbook on Twitter and I'll alert you to free downloads of the forthcoming volumes; or click the Following button at the foot of this page.)
And if you have no objection to such promiscuity, Like this.

Freebies (Teaching resources:  nearly 33,500 views**  and  4,600 downloads to date. They're very eclectic - mostly EFL and MFL, but one of the most popular is from KS4 History, dating from my PGCE, with 1637 views/740 downloads to date. So it's worth having a browse.)

** This figure includes the count of views for a single resource held in an account that I accidentally created many years ago.