I always CC in the AIWB mode and only once (that I know of) have I ever been "made". We looked at each other (She went from my eyes to where she saw the gun), I said "Good Morning"...she said nothing so I continued to shop at Home Depot. I do my best to wear long enough shirts that even while lifting my arms it's not exposed, that said, I'm not going to freak out, I'll play it off as no big deal (because it isn't a big deal) and go about my business.
If someone wants to cause a fuss, that's on them...IMO.
You bring up an old memory from the 90's when I was in a hotel in NYC and ran down the hall to get ice. I had already taken off my suit jacket and oddly forgot as I went out the door. So I am cruising down the hallway and come upon a couple at which time I realize I'm wearing my gun. Attitude is everything. Look like you belong. They didn't say a thing and didn't report it. Two reasons of course are that this was a high-end hotel at which plenty of people with private security were staying, and I was well dressed.