My solution to this problem, (about 28 yrs ago) was to take the butt stock off, shave 3/4 in. off, and while I had the butt-plate off I took it over to the neighbor. He was a Master Cabinet Maker, and I had him spend all of about 5 min. hogin' out the inside of the stock, and then we poured in about 1.5-2.0 lbs of # 6 shot (what he had laying around) we then poured hot candle wax over the shot about 3/4-1 in. thick (filled the hole), and put the butt plate back on. The shotgun still tracked good, extra weight being to the rear, and the recoil was a lot softer. There was still a bit of "whip" or barrel rise to it, but the actual "shoulder pounding" aspect was gone.
It worked very well for me, but YMMV