Having worked undercover a number of years,(82-97) I always used to carry my weapon in an “unusual” carry to avoid detection and/or being “burnt”.
The weapon was carried up-side down (slide toward ground), barrel horizontal, centered of the belly, just below the belt-line of my pants.
This position afforded a quick access, yet difficult for “bad-guys” to detect in a “bumb” or “brush” against me. (it’s normal reflex for a person to cover his belly with his hand rather than his side).
I was even searched by uniformed officers on 2 seperate occassions who failed to detect the weapon. One even did the old text-book procedure of inserting his thumbs inside the waist-band, but failed to make them meet in front (where he would have felt the butt of the pistol).
Now as a training officer I make it a point to stress this simple tactic to new officers. Because usally the gun they might miss will belong to a bad-guy not a narc.