My current rig is much smaller and am about 50/50 with setting off walk-throughs and wands. I am always prepared for it to go off. Someone said it's about confidence. To me that is 90% of it. The other 10% is where it's located at on your body. I have also just put my pre-amp with my phone a couple times and said it's for amplification for my hard-of-hearing self.
They are looking for weapons almost always. Not a tiny recorder and mics.