I've done a backup to FTP of all of my VS on my old VMPro server with a disk that is dying. I've built a new VMPro server with the same configuration. I try to restore the VS backups and the process fails at the first VM telling me that it could not set quota for the Administration user. I'm dry-running this today and plan to do the real backup / restore on 1 Jan.
I followed the process identified in http://www.virtualmin.com/documentation/system/backup-and-restore for "Using Backups to Transfer Virtual Servers". It appears there is information that needs to be transferred to the new server before I can do the VS restore.