we have Lodge of Instruction for a certain degree maybe once a quarter, and it's around 10-15 people.
floor school can get busy at around 15 or so working on the degree, and then there's always people in the library working on memory work as well (4-5 more there)...
the key is to offer pizza. get those tony's pizzas that are like 2 dollars and cook like 4 of them. people will come and eat them and then stay because they feel guilty.