FWIW, G. T Thomas played around with headspace (depth of rim cut) and determined that a slightly deep-cut rim can elevate perceived recoil.
I had personal reason to look into this some years ago with a project gun that had rather deeply cut rim recess and found distinctly less perceived recoil when rims fully filled recess than when they only filled it about 1/2.
I am one of those folks with shoulder injuries that make me much more recoil sensitive that previously. In addition to usual dimensions of good gun fit to me personally, actual curvature of buttplate, both vertically and laterally, makes a big difference, as does having buttplate that does not slip on recoil. Buttplates that are flat horizontally are worst -- they really "bite".
Like many other shooters, I find my scores at 16 yard trap to be at least as good with 7/8 oz, 1200-1300 fps loads as with any 1100+ fps 1,0 oz load. This is heavily a matter of felt recoil. A couple of rounds of trap with 1,0 oz loads is about my practical limit, whereas, 3-5 is OK with 7/8 oz loads. All of this presumes I am wearing a PAST ambidextrious recoil shield.
Niklas