Why don't you try varying the nights... Guest performer and support one evening.... singaround for all comers another evening where all sit round the room and sing from the seat they are in..... Open Mic night where the performers have to take stage at one end to perform in front of the crowd........ Why make your Folk Club nights exclusive altogether to some.... after a while of varied nights you can judge which nights are bringing most people in/causing most interest and maybe increase the number of those nights.... Just don't rush into anything you might regret. Best wishes, Mike.