I bought a MagPul MS3 with a front QD and just plain strap on the back and put it on a 11723. It’s amazing. I removed the crappy female QD that came with the gun and added the three rails on the new forearm and put a female QD on the left rail piece. And then I just threaded the strap around the base of the new collapsible stock. I’m a right handed shooter and put my left arm through the sling and have it rest on my right shoulder. A simple adjustment allows me to carry the M4 (in entry configuration) across my chest in a port arms type style with the muzzle facing down. I can quickly and easily bring the M4 to firing position - and if I’ve set the tension on the sling just right, I can rest the sling on my left arm to increase stability of the shooting position.
This worked so well when I was at the range today I stopped at a LGS and picked up two more of them for other guns.
Shotgun tactics and usage are much different than pistol or rifle tactics and usage imo. I've never seen the benefit of a detachable mag fed shotgun, only liability, as least for stand alone use with no backup or support. I like to be able to top off the magazine on a shotgun on the fly. IMO detachable mag fed shottys are not nearly as versatile as tube fed mag, if for nothing other than to be able to immediately switch loads.