To get back to a comment by OCB - how did he use this rig horseback, it looks very awkward to me. Set low it would be difficult to reach cross draw, unless lft. handed using a reverse draw, and why a reverse draw - why not strong side? And a rig like that worn low on the body does not provide much security when riding rough country at speed.
Although from the east I had a chance once to go elk hunting in Wyoming with my sharps single shot, a horse, and a bedroll for a week. Since we were in Grizz country and we carried the sharps across the pommel unloaded, we both packed a SAA pistol, mine 5 1\2 inch - figured I'd use mine to really piss off the bear while my horsed pitched me toward him on his way outa there. Anyway I had a week to fool around with where to carry the pistol on my belt, it was carried in a deeply recurved rt. handed slim jim that could be slid anywhere on my belt. I settled on just in front of my left hip. Even without any tie down for the gun, it stayed secure, and was easily accessed if needed. Even riding in the dark I could always sense the butt of the gun against my abdomen letting me know it was there. Something I could not sense when carried strong side on my Rt. hip. Of course my belt was worn fairly high on my waist allowing comfort for riding. Even in CMS riding like the dickens with quick turns my cross draw gun worn like this always stays secure. However, my gun is worn up high, owens is worn very, very low.
The point being, old perry owens who knew a site more than me about guns and horses, is wearing a rig that just doesn't make sense if the two need to be combined. I considered Marlin's comment about throwing the rig around the saddle horn and putting it on when you need to, but that huge rig placed in front of the rider doesn't make sense to me, either from a comfort or security standpoint.
At least the photo of the Arizona ranger shows him with a shorter barreled gun wearing it on the strong side, not slung so low. That would be comfortable, if not all that secure. Maybe someone with more experience than me wearing iron on old dobbin can throw their opinion in here.