I'v done the whole stash the sack under the sack thing before, usually when i'm getting pulled over. I DO know for a fact that putting it under the balls wont work if your walked through a full body scan machine, There designed to pick up FOREIGN objects , examples are hip replacements, screws, spikes, plastics, steel plates plastic plates, condoms filled with cocaine in that you swallowed pre flight. and sacks of weed under the nuts. And I think it's called S.S.S selective security service and it usually picks peoples numbers randomly, but every time i fly i am chosen, weird huh . And with the patriot act into effect, I dont even want to know what they could do to you for it. you NEVER want to be made an example of. Be smart man use your common sense.