I wear overalls year around and carry a Glock 17 in a Blackhawk Serpa holster. I wear light shorts with a belt under the overalls. Button up the sides, and no one will know you are carrying. If you then believe a situation calls for it, you can unbutton for easy access.
Have you tried to draw your gun this way? What about under stress in a class?
Lifting a winter coat up to draw is hard enough, but unbuttoning the side of your overalls to draw your gun?
Yeah, I ain't doing it.