My current poetry-project (after completing 10 sonnets, which was my last one) is to translate the five boks of Psalms from the original Hebrew to English in iambic pentamater (with occasional trochees when I must - as long as it sounds good).
Luckily, I'm fluent in Biblical Hebrew - and going on towards native understanding - so the language is not a problem; I also happen to have possibly the best commentary ever on it: my problem is not that, rather the English phonetics.
It never happened so much before that I took notice, but for the meter's sake I'd rather show a difference between "fear" as a single syllable pronounced "feer" and "fear" as two syllables pronounced "fee|ər".
My father recommended I write "feär", and "bithéd" if it's pronounced "bir|thed" - which it was in some case. So the rules are:
1) Put siareses when two combined vowles are pronounced individually.
2) When as usually-suppressed vowel is pronounced, put an acute.
But how do I mark two vowels that are supposed to be said as one, assuming there's no ligature such as "æ"? Using a breve over one of the two?
And what other marks should I put to clarify? In Milton's day there was flexible spelling, and he used it carefully; what do I use?