"I don't see how an accurate assessment of middle English pronounciation can be made!"

Why worry about it? Isn't it more important to keep the poetry alive than to wonder if I'm pronouncing a vowel right?

If you change the vowels from 'ay ee eye oh you' to 'ah ay ee oh oo' (which is what most of the Western world uses) and keep the consonants the same, you will be close enough. In fact, you might be doing it right.

There will be a few exceptions and hiccups - words like knight or cough - but they are not important in my view.