I did try this tonight with my server. It did not allow more than 4 people to join, even though the server showed 4/8. I tried every means of connecting (driect, steamgroup, invite, etc). I thought maybe it was due to server reservations, so I installed Downtown's unreserve plugin. Before I tried it, I remembered that I had allow_lobby_connect_only set to 1, so I changed it to 0. When I tried this time, it worked fine. I'm not sure yet which change allowed it to work. Thanks for the plugin.
Any chance of making it so it will not spawn bot players? It would be nice to only have survivors spawned if there is a human to control them.