Never been to any cosplay event but I think that's usually why they do use cardboard or foam. Almost anything "could" hurt anyone and I'd be surprised , even being mild and probably not sharp, that they would let him in one of those events with and metal, metal weapon. Just a thought from someone who was turned away from a ren fair wearing a SSO in a sheath. Wouldn't peace tie it or anything just made me put it in my vehicle. Just a thought. I'm not against it . Society just seems like they want it padded and overly safe. They even got on my case when I made a wooden pirate sword with an aluminum guard. I painted the wood silver so to them it looked too real can't have much fun anymore.