There is no way to say rank 3, 5 and 6 can see this page/message/forum/etc ...
Not yet anyway.
lol
funny I have sickening memories of trying to deal with this when I was coding >.<
I was essentially, instead of storing member ranks in the profile area of the database, I had a 2 column category with USER_ID, and RANK_ASSIGN ... so that I could assign each user to as many ranks as I wanted to ... thus allowing them to see through, or around different ranks ... In the end I scrapped the idea and was heading more towards what you have now ... sometimes you just have to say, ok. This thing can't do everything ... lol pick yer poisons ^_^