we had a successful 40ish players attend Chimera Con last year to play wargames and more complex/long-play boardgames. We had pre-registration for most games but I kept about 25% of the space for free-play games.
In the end we didn't really use the free-play area as instead we absorbed floating players into the games that were already running.
I tried making a geeklist for people to advertise their free play games but that got little traffic.
I wonder does anyone here have experience of how to get good utilisation of free-play space?