Beyond 25 yds has seemed to be the land of diminishing returns for me as well.

I would add that I hand load for all my vintage 16’s both spreader discs and X spreaders. I also always use Jay’s over layer of shot on the discs. Consistently, I get a more open pattern with the discs than with the X’s which is nice for the guns that are choked F-F.
Disc in the RB, X in the left.

And no complaints about pattern uniformity with either.

Speude Bradeos