[Dovecot] Want to have some users with Maildir, some with mbox

[WJCarpenter]

> http://wiki.dovecot.org/Migration/MailFormat shows a bunch of scripts, one of them claims to preserve UIDs.
>    

Does anyone here have direct successful experience with this?  I only 
asked about this because a comment on that same page says, "None of the 
solutions described below preserve the message UIDs."

(Some of my users have > 1 GB of email, so any UID disruption would 
likely be seriously annoying to them.)