depends how long and flexible their dicks are.
also assuming everyone is standing up. If there are platforms to lay in, could change things?
even the most flexible dicks wont bend 90* and work like its supposed to. If each connection can get you a 15* you could get by with 24 guys. Of course this is also assuming straight dicks that then bend. If you find a group of guys with dicks all bent in the same direction, that could really lower the number. Say you find 12 guys with 15* bends already, get them do go at another 15*, that could close your sex circle.
so Im gonna say 12-24.