Backup using BackupPC

I have managed to install BackupPC in my LAN and am currently backing up my mail server that is in the DMZ. The problem that I am having are the permissions on new .gpg files created during the backup - the user and group are set to user-data:root and permissions do not allow anybody but the user to read/write. I have setup BackupPC to use the user backuppc to do everything. I have changed the directory and files ownership to user-data:backup and allowed the group to read the files. I can then do the backup. Now each new file created by the backup agent on mail-in-a-box has the old permissions and ownership. Is there any way that I can change this so the group backup has read permission automatically.

Thank you again

PS: if anybody would like to have the installation instructions I can post them if you like

Hi - anybody have an idea what to do?