Not possible to replicate from 2.3.7 to 2.3.16?

[Jason L Tibbitts III]

I'm trying to move my mail services to both new hardware and a new Cyrus
version.  This involves a change in architecture from i386 to x86_64.

I was going for what looked like the simplest method: set the new server
as a replica, let everything replicate, then quickly shut things down,
configure the replica as the master and switch IPs.  Unfortunately I'm
stymied at step one; replication seems to fail.  Simply running
sync_client and trying to sync one user:
  /usr/lib/cyrus-imapd/sync_client -S util1 -u tibbs
yields (on a completely fresh installation, with no existing mailboxes):

Mar 27 00:10:32 util6 sync_client[32618]: Doing a peer verify
Mar 27 00:10:32 util6 sync_client[32618]: verify error:num=20:unable to get local issuer certificate
Mar 27 00:10:32 util6 sync_client[32618]: received server certificate
Mar 27 00:10:32 util6 sync_client[32618]: starttls: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits new) no authentication
Mar 27 00:10:32 util6 sync_client[32618]: USER received NO response: IMAP_MAILBOX_NONEXISTENT Failed to access inbox for tibbs: Mailbox does not exist
Mar 27 00:10:32 util6 sync_client[32618]: CREATE received BAD response: Missing required argument to Create
Mar 27 00:10:32 util6 sync_client[32618]: Error in do_user(tibbs): bailing out!

The replica machine says:

Mar 27 00:10:32 util1 syncserver[12709]: Failed to access inbox for tibbs
Mar 27 00:10:32 util1 syncserver[12709]: cannot unlink /var/lib/imap/user/t/tibbs.seen: No such file or directory
Mar 27 00:10:32 util1 syncserver[12709]: cannot unlink /var/lib/imap/user/t/tibbs.mboxkey: No such file or directory

I note that after this operation, the mailbox ended up being created,
probably because of the autocreateinboxfolders setting.  (I'm running
the Fedora packages rebuilt for RHEL5; they seem to be pretty closely
based on Simon's.)

So, is it expected to be generally possible to replicate from 2.3.7 to
2.3.16?  If so, would anyone have any idea what I might be doing wrong
here?  If it's not possible, would it be reasonable to migrate initially
using 2.3.7 on the replica and then update to 2.3.16?  (I'm trying to
avoid downtime as much as is possible.)

 - J<