Retrieving Mailbox Folder Information from an RDB

Hi all --

I'm looking to do a New-MailboxRestoreRequest to recover some specific folders (deeper than top-level) from an RDB mailbox to a production mailbox.  However, before I initiate the restore, I'd like to verify that the production mailbox has enough space to accommodate the folders I'm restoring.

Obtaining folder size information from production mailboxes is straightforward, but I haven't yet seen a way to do it with folders in an RDB mailbox.

I'd like to avoid having to use MAPI and keep this to PowerShell cmdlets if at all possible.

Any help/clues appreciated,

James Mooney, EMC Corp.