Why not specify 2-3 problems? Won't you have people show up having already spent a bunch of time on their self chosen problem? Which sort of defeats the point of seeing what you can do in a short period of time?
We allow prior work as long as it's labelled. We record chat logs, so it's easy to verify what's prior work. When we evaluate the significance of a result, we focus on the part produced at the event.
just something to think about
Good going, hope it goes well.