Yep. If they want to put only themselves in danger in a Closed-course situation, I say Go For It. I saw the Streetfighterz in St Louis once. They had a waist-high fence blocking off their play area. More than once they almost came through the fence, putting the on-lookers at high risk. I had to take my daughter and leave because I felt they were not as in control as they needed to be.
