The first haunt I ever worked at would send down groups of 20 or more..there is no way I ever do that again. It was scaring on a conveyer pop out repeatedly hit the group a few times and then get ready for the next thought, no art, just get in there and scream at them. Now we do groups maybe 6 if pressed, but we normally try 2 , 3, and 4 . Families , friends all want to go in together..but a skilled " herder " can get them to divide most of the time. If you have people complaining about a long wait then think up something to entertain them while they wait. Roamers, a live band, gift shop, concessions, quick skits, videos..lots of things out there that can be done to help break up the monotony of standing in line. I recall an episode of Supernatural where the new lord of Hell was describing how he changed the place , made it more streamlined...Hell is now one long wait in get to the end of it finally and your shot to the back to start that scared me !