Still wouldn't recommend it though. Not a lot of people are playing mafia nowadays. I would say my 21 player sign ups filled quickly because everybody is familiar with the theme. I dont think everybody watches South park and family guy and I don't think TB has 35 active mafia players in general.
Well yes number of players is dependent on the theme too.
But in the case you have a theme where you can get lets say 40 players. You should make a game as big as you can handle it. If you think you can do 15 players, do it. If not go low.
I personally think 15 to 20 players is what most new hosts should aim. Not bcs of the number of players but more so because big games require a lot of focus and even best of hosts can loose it in bigger games