I started keeping a WML on my gun 24/7 many years ago. I wanted a shoulder rig for the times when it’s a better option (like 17hr road trips). Not wanting to give up my WML I had Coffman Concealment make this. He used a Galco harness. The muzzle are was left open so it works with a G19/17/34.
I also have back issues which is why I went with a perfectly balanced set up.