migrating mails between two cyrus servers keeping seen states

[Marcus Schopen]

Hi,

I'm planning to move some mailboxes from a cyrus server (2.1.18 - which
is a kind of mail archive) to another one (2.4.17+caldav~beta9-3).
Playing around on a test system with copying a user's mailbox and doing
a following "reconstruct -r" came out with a mailbox without seen states
on read mails on the new system; all mails unread. Normally I move
mailboxes using imapsync to keep states etc., but on a number of really
large mailboxes the initial sync takes days. Any other suggestions than
(slow) imapsync tools?

Ciao!
Marcus