changing mailboxes in DB?

hi.

I need to move/ merge a lot of mailboxes and was wondering if i 
could/should do it directly in the DB (updating the mailbox_idnr field 
is easy, but there's also seq,.. and i assume that should be updated 
too?

has anyone done this before?

-- otherwise i guess i'll have to do it through imap which is slower, 
but doable since it is only one user and a total of 3721 folders (which 
i am trying to get down to a reasonable amount since all webmail clients 
go either really slow, or time out)

Regards