I'm trying to develop an intranet site which will have group forums, wikis and maybe blogs. The design calls for some stuff to be visible to all members and other stuff to be restricted to some goup(s). It looks as though OG is just what the Dr. Ordered. I think I have a pretty fair grasp of Drupal users, roles and permissions. What I'm having trouble getting my head around is how OG users, groups and permissions interact with the drupal equivalents.

e.g I can't figure out how to get an OG group admin the ability to create a forum for her group. Does this require creation of a group admin role in drupal? It seems I can only get that ability for the OG group admin if I check administer forums permission in the authenticated user role in drupal . Somehow, I can't believe that's the way it's supposed to work, cause I don't want all authenticated users to have that permission.

Is there anywhere I can find some real documentation for OG that will get me pointed in the correct direction?