ducktapehero
I am sorry to hear of the surgeries and nerve damage. This makes matters more serious for you and my concerns are what the Surgeons have to say- for now and later years.
My thought based on folks in similar situations -
Mercury reducers do help to a degree. They do add some weight which will affect the balance , which in turn may affect gun fit. Gun fit as you know helps a lot with felt recoil .
I really like the P.A.S.T shooting vests and shoulder pads. You "may" need to take these into consideration on the gun fit when using because LOP will be affected.
I know some folks that HAD to go to .410 only , I mean the Doc showed and made clear what would happen if disobeyed. I know a few allowed 28 ga and no more. I'm talking about using a 1100 in these guns as well.
Which brings us to the gas gun, like 1100s .
Granted the 12 ga is the most versatile, and in a pump gun the 7/8 oz loads are soft recoiling ( Rule Of 96), these loads may not run in a gas gun.
In some 20 ga guns these 7/8 oz loads "can" have a sharper recoil ( that rule again) say in a O/U. In a gas gun , say a 1100 in 20 ga the felt recoil is very mild.
Buckshot and Slugs...going to have recoil no matter what .
I would try someone's 20 ga 1100 and see how it feels. Borrow a P.A.S.T vest or shoulder rig and test.
They do make a stock that "gives" with the recoil , I forget the name, expensive, and one has to be concerned with gun fit just the same. IIRC there may be some concerns on the adjustment and the loads used.
Dave, kudu , PJR ...will know the name of the company.