A Star Trek holodeck presents an illusion of a location to users who are inside the room.
When the party splits up each group sees that the other group has moved away, but in reality they're in a medium-sized room on the ship.
The assumption is that the holodeck tech is able to present a different illusion to each user.
So, how many real tangible users could fit inside a holodeck and not spoil the illusion? Could it be as small as the Da Vinci radius around a person?
Assume normal sized humans between 4 and 7 feet tall, with normal proportion armspans. Its reasonable to ignore extra senses like Geordi's visor or Seven's extras, or any sense that a non-human might possess.