A note on setups:
7 players is perfect for
C9, even with its slight balance problems
9 players is perfect for the latest tested version,
2of4.
F11 is also a good option for a more tested but less balanced version.
A smaller game with 5 players can utilize
Dethy, which is a fun chaotic game.
In general, there should be either floor(n/3) or ceiling(n/4) mafia, where n is the number of players in the game. Note that these are only different if n is a multiple of 12, which is an unlikely scenario.
Another note: Using chat messages as a way to determine power roles/mafia is a very despicable strategy and should never be used. An easy fix is for all players to send themselves some private messages during the night, but this will only work if everyone does it. I highly suggest it.