[Dovecot] Migration from v1 to v2 with hashed directory structure

Hi,

I want to upgrade to version 2 but I would like to solve a long standing problem with 'flat' directory structure ie we have /var/spool/vmail/mydomain.com/user@mydomain.com and I want a new server with version 2 to have hashed directory structure like /var/spool/vmail/mydomain.com/u/s/user I was wondering it f there is some better solution then dir hashing or a way to hash a dir other then first two letters. Also any suggestion how to perform this migration from old to new server with hashing on the fly?

Thanks in advance.