The whole 'less people' thing is standard for any maze to be honest. The less people there are, the more time the actor can devote to each person, thus improving the experience. Also, there's less time between the front and back, thus adding to the surprise. Being in a group of say, 10, and being at the back, and hearing the person at the front scream, the scare will be ruined. Being in a group of 4, you will experience the scare at the same time.Simples.