i think anything above sixteen is ridiculous for gameplay reasons still
I like 16, too, but I can live with up to 18, as long as everyone there has played before and knows what they are doing. And I believe 18 is the minimum amount of players you can have for there to be 5 mafia. This, however, only happens occasionally because you don't always have 18 active players in one round. I like for there to be 5 mafia every once in a while.
Anything above that becomes too hectic for me and it's way too difficult to keep track of numbers and bodies, and sometimes rule-breakers.
i mean, it is mafia madness, not mafia snore or whatever
And I don't think the madness should stem from the chaos that ensues from there being 22 people in a round. It should come from the confusion that the mafia create, or that the innocents create accidentally.
Also, the higher the playercount, the higher the rule-break count, in general.