This is a question for those who've tried it...
I know the game says 2-5 (ie Keeper + 4 investigators). How difficult would it be to add a 5th investigator (ie 6th player) and keep the game balanced? Would giving the keeper increased threat, or somesuch, work? I've got a group of 6 players that the game would be fun to play with (3 sets of couples) and wouldn't really want to leave anyone out of the game.