What you say about pinyin u and ü works fine for me. But I want to ask about a variant on ü that I sometimes hear, for example in John Pasden's tone drills. It seems the speaker has a more extreme pronunciation of ü, so that 军 rhymes with the English word queen. Even 去 there rhymes with the English tree. Is this a regional thing? Or do you think I am just mis-hearing those speakers?