My local sing around crayside folk club usually has under 20 people . It's about the right size IMO , so every participant usually can do 3 songs if they arrive early enough. We have a range of abilities and styles, and everyone gets encouraged and appreciated. There are other punters around often that seem to appreciate us there , though not always actively listening. One slight gripe is the occasional player who spend the time they are not themselves performing, on their phone , but at least they are quiet ! Hardly any rules, though participants are not expected to play the same song three weeks running .there's no charge but an optional raffle.