I'm not sure how I'd go on this issue. I teach a small group of adults at the Y and at a public park. Anything like open sparring would not be allowed at the Y. At the park, guys we knew from other styles would come in and mix it up with a couple of younger, more experienced students of mine. It was a positive experience... and fun. But I already knew these guys. They were good at what they did, had control, and didn't have any serious ego issues. I wouldn't be comfortable opening up sparring at a class in the park to any stranger who walks by. We get all kinds wandering past. Some drunk or on drugs, and out here a lot of guys carry concealed knives and guns. No permit is necessary. Tempers flare and things go bad. I'd rather get together with other individuals and groups I know. Or at least check the guy out very thoroughly. Maybe I'm just getting old and overly cautious?