I don't know of any official policy, but I saw a stage presentation (Shear Madness, maybe?) there once, and the whole setup was pretty ghetto (bleachers or something similarly uncomfortable). Definitely wouldn't need more than a nice dress-casual shirt and khakis. I would recommend wearing layers and/or a jacket that is easy to remove. I always find these things heat up as the show progresses, until I'm so uncomfortable I can barely sit still and want to run outside screaming.