3.5" is good if running steel on geese.
I've used BBB standard stuff successfully, but I've lost a few birds to it, and many aren't dead when they hit the deck (require a ground swat to keep them out of standing corn or a grab and twist).
Most shots 35 yards and in.
Have not tried Black Cloud or Blindside in 3.5".
I switched to Bismuth 2's in 3" and hammered geese dead to 50 yards. Works waaaaaaaaaaaaaay better. But damn 'spensive. Especially now.
I have an 870 Supermag. I run 3" lead #4's for turkey, seems a good 45 yard and in load (WW JV's in a Superfull choke). For geese I might try steel Blindside 3.5" BB with a modified tube- got a box, dunno if it will be better than my past experiences with steel and honkers.
If it sucks, then back to Bismuth 2's in 3"- and an 1100 magnum, the 870 supermag then a loaner
Ducks I ran #1 steel way back, took a few, worked fine. I switched to geese only after that, as my spot was much better for honkers and the meat yield more............plus I shot them over the dry land section of that farm