Advice on seen status migration

[Robert Baldwin]

I am working on a script to migrate users from an standard Cyrus 
installation to a Kolab server installation.
On the source IMAP server the users have simple usernames ie: testuser1 
whereas on the Kolab server these users are migrating to a full 
username, ie: testuser1 at example.net, due to this change I believe I 
cannot simply point the Kolab server at the old Cyrus spool folders.

I tried making my script execute imapsync to perform the mail transfer 
but found it is really slow and I found it to be unstable.  imapsync 
would occasionally exit in the middle of migration with no indication of 
error.

My alternative is to copy each users Cyrus spool folder from the old 
location to the new Cyrus spool folder beneath the Kolab folder and 
perform a cyrus reconstruct, however that leaves seen/unseen status 
un-migrated.   Does anyone have any tools or pointers for migrating 
message seen/unseen status?