^ what he said.
I make stack tapes most of the time I stealth. Using the omnidirectional DPA mics listed in your signature, you'll probably also want to get high sound pressure levels in order to drown out crowd noise and ambiance (espcially if the room/PA/sound engineer is not particularly great), so I would definitely try to be as up-front as possible. But do walk around and check out different spots. I find ear plugs extremely helpful, because to me, what I hear with ear plugs usually comes a lot closer to what the tape will sound like. And of course it's better for your hearing anyway.
Also, beware of the typical walk-through areas, close to the bar or the bathroom for example. It sucks to constantly have people tapping you on your shoulder because they're headed for the bar and you're blocking the way...