Some "sex clubs" have pre-entrance requirements, but they're usually about looks and build. For instance, some guys have to pull up their shirts if they're suspected of being fat. If nudity's involved, girls can make up their own minds about size. As I remember, my normally awesome pickup rate used to plummet dramatically in clubs where the clothes came off.
But I've been out of the scene since getting married, so things may have changed. Who knows? They may have a "Hung Night" now, like some clubs used to have a night for gays. Come to think of it, that could aptly be described as "Hung Night".