If they are not supplying us any, I believe 3 would be good. I think that's what we had last time and we still had plenty of room.
An update and an idea for those coming. I won't have the Halo Ring fully up and running by the time the con rolls around. Too much side work going on to dedicate that much time to the project. I can however have it ready to work on the interior of the ring. Adding all the little details like islands, land masses, clouds and mountains. You could make your own little section on the ring to call yours when it's all finished.
Does this sound like something we could do to pass some time working the booth? Let me know, and I'll bring the ring.