The game designers behind the rooms at Fox in a Box - Chicago have done a lot of research into "optimal team size" and our rooms are built accordingly.
In an ideal team, every person counts. Studies have shown that once there are more than 8, 9 or more in a team, communication and collaboration become cumbersome and the team tends to break down into sub-teams. As teams get larger, there is a tendency for social loafing where some members get to slide and hide.
This is why our private rooms at Fox in a Box - Chicago are built to allow a maximum of 5 to 7 players. We want each individual to fully enjoy their experience and to feel like they've played a meaningful role in their team's adventure.
The maximum number of players per room are as follows:
Bunker: 6 (but can include a 7th player if necessary)
Zodiac (must be 18 yrs or older): 5
Final Exam: 6 to 10 (people are split into two groups playing two Final Exams head-to-head)