It's an awkward one. Performances like that are deliberately done to look dangerous, and there always is some risk, but if the performers weren't good enough to reliably pull off their performance successfully, multiple times per day for weeks on end, they wouldn't have a show.
For something like that, a d20 roll is probably too granular. Even with only a 5% chance of a performer taking a serious injury per show, you're probably looking at too high a chance of the troupe being unable to perform a full several-week run of their act.