NFS access to OwnCloud data folders?

Is there a way to enable NFS access to the Owncloud data folder with a login other than admin or root?  The owner:group is set to guest:guest, but the admin UI (this used to be called Frontview, does it have a name in OS6?) does not know of group "guest", so I can't add myself to that group using it.  If I add myself to the file permissions, OwnCloud refuses to present a login screen, protesting:

Data directory (/apps/owncloud/web/data) is readable by other users

Please change the permissions to 0770 so that the directory cannot be listed by other users.

Is it safe to add myself to secondary group guest via SSH with usermod -a -G?  ReadyNAS group members don't seem to be listed in /etc/groups, so I'm unsure if that is safe and/or effective and I thought I'd see if anyone knows before I just go and try it.

Maybe this is for it's own protection because adding files without going through OwnCloud itself will mess with the database.