I've tried out this great extension, but there are a few flaws with it.
I actually did manage to get more than 8+players, but after 8 players were in the server, no more people could join. Sv_visiblemaxplayers was set to 16, but they still could not join.
It seems to be totally controlled by the map, as I was playing a survival map and people couldn't join in with 4+ players. Some of my players tried joining via "connect ip" but still couldn't join.