Sad to say Coosa, is that most S X S shooters don't even know if the loads they're shooting regulate in their S X S gun. I've found that lots of vintage S X Ss prefer a certain payload at a certain velocity, and loads a lot faster, lighter, etc. will NOT regulate, but will crossfire badly, or vice versa. I'm certain I have several that would not even come close to being regulated with 3/4 oz. loads, at any reasonable velocity.
I've never patterned light loads in any of my SxS guns, but I have tested 8 different guns with the heavy TSS turkey loads. None of them would shoot either barrel to POA. In 7 of them, the right barrel shot to the right and the left barrel to the left. One kinda cheap Spanish gun cross fired every load that I tried in it. It was made in the 60s, but looked new. I suspect that everyone who ever owned it couldn't hit a thing with it and gave up using it. It had fixed chokes, but was worthless the way it was so I took a file to it and got it to shoot a TSS load straight. It's now my backup turkey gun and has killed several turkeys. Of course, that load is the only thing it will center.
My theory is that a SxS gun can only shoot one load perfectly. The results might be acceptable with other loads, but only one can be right.
