Urgent: Downgrading from 6.X to 5.X?

[Francisco Reyes]

How can I downgrade from 6.1 Stable to 5.5 Stable?
Having all type of problems with NFS. Both with the server and the client.
>From what I read on the stable list others are having simmilar problems, 
but don't see any mention of fixes.

I need to downgrade a number of machines from 6.1 Stable to 5.5 stable

What do I need to do?
cvsup to 5.5 stable?
On the archives I see mention of a delete flag to cvsup.
Do I need to do one run with "cvsup -D" and then a regular pass?