thanks to advice from our resident tso's ^ as a result of this (http://www.flyertalk.com/forum/trave...chine-lax.html), i always ask for individual swabs for my shoes (and the same for my hands if they are getting swabbed as well). i simply ask politely and give the reason that i had a prior false positive and fwiw, only once did i get attitude-every other tso was very cool with it