Since the original request was made in 1996, I feel that I can safely make a remark without hurting Pamela's feelings.

Remember when I started a thread about English lyrics with many consonants in a row? It had to do with a Chinese friend and with preparing hymns for people who cannot read well.

Surely 'couldst thou' with its dst-th is notable in this respect. Not to mention that the vowel sound in 'could' is not our most straightforward, either.