[Dovecot] two concurrent dovecots

Hello,

Is it safe to have two concurrent dovecot processes to access the same maildir? I have a stock RHEL version (0.99.11) used by users, but I also want to test 1.0-beta together wth postfix for SASL. Is it safe to access the same maildir concurrently with both dovecots (say, the old one via webmail and the new one via remote client)?

Thanks, Alex