[Dovecot] Migrating to dovecot configuration questions

[Adam]

I am currently running a mail server on an earlier version of Red Hat 
Advanced Server, sendmail and UW IMAP (imap-2007e). I am considering 
changing to Dovecot for IMAP but have a few configuration questions 
in regards to a hashed directory setup.

Right now the mail spool for everyone's mailbox is located in 
/var/mail/first letter of email address/second letter of email 
address, for example ajaym would be found in /var/mail/a/j ,email 
address john would be in /var/mail/j/o  and so on.....

Most users using IMAP have a home directory where they can store 
their personal folders, trash, sent items, etc.. in /home/username.

I am looking for some configuration information on making  a smooth 
transition from UW IMAP to Dovecot and keeping the existing directory 
structure.

Any info or suggestions??

Thanks
Adam -