[Dovecot] Public (Shared Folders) ACL Questions

I'm trying to set up a public namespace so that a set of IMAP folders are available to all staff - similar to MS Exchange Public Folders.

I've managed to set up the namespace correctly but I'm having trouble with the ACLs. The global ACL file is the only method I can get to work.

All I want to do is to allow 1 user admin privileges to create & delete anything but all other users should only be able to create not delete. Reading through the mailing list I thought a /etc/dovecot-acls/.DEFAULT file would be suitable but what should be put in here to achieve what I want? Are you able to use wildcards somehow within this file, i.e.:

owner lrwstiekxa user=admin@domain.com lrwstiekxa user=*@domain.com lrw

Does this .DEFAULT file only apply to the public (shared) namespace or will it effect private mailboxes also?

If I was to create a specific global acl file for a specific folder which would take precedence, the .DEFAULT acls or the specific folder acls?

Also an "INBOX" is shown within the public folders namespace but no folder exists in the public folders maildir hierarchy - any ideas how I can stop this?

Any help would be greatly appreciated.

Gavin