2 3/4” shells will work just fine one could even argue with less recoil it’s easier to stay on target for that follow up shot. I would keep the shots closer with that slow of a steel load however. But 1 1/4oz is a pretty standard load weight. Personally I have come to like 1 1/4oz at 1500fps, 1 shot, 3” out of a full choke. It’s simple, more shot+ more speed equals more likely to crunch ducks. you could drop a goose at 80 yards if your shell only had one pellet in it if you got lucky enough. I hunt the big river and most shooting is hitting birds on the inside corners 30-45 yards, not feet down. 3 1/2” 4 shot is a great shell to keep in the pocket for taking cripples to pound town.