I will give you two thumbs up for the Cross Breed Supertuck (
http://www.crossbreedholsters.com/). I carry a Glock 26 in a right handed Supertuck daily and my spare magazine in the Cross Breed tuckable magazine carrier. I have all of that on a Wilderness Tactical 1 1/2" Instructor belt along with a flashlight, Leatherman, cell phone, and work phone.
This a great rig and I was fortunate to find it before I spent hundreds of dollars finding a setup that works, is coomfortable, and is secure. There is no retention in the holster except for the gun specific impressions in the kydex panel of the holster. When you are wearing it, the gun is pinched between your body and the Kydex and the gun is firmly and securely held in place.
I do wear this holster with a shirt tucked in, and it is comfortable and well concealed. The adjustability of the belt loops is what makes this holster so concealable, and I am able to have the gun held with the butt tucked right against my side. It is comfortable all day long and I usually wear it for 14-16 hours a day. In places where I can't have a weapon, I just remove the gun and mag and continue to wear the holster and carrier. The holster stays open so replacing the gun is easy.
I highly recommend this rig. If you need another reason to buy it, my same holster will also carry the G17 and G19. I am unsure if it fits any of the .40S&W Glocks, but I am sure Mark at Crossbreed could tell you.
Give them a try. Idoubt you will be disappointed.
-Matt