There's several after-market manufactures of choke tubes for waterfowling. Steel shot through a modified choke will pattern tighter than lead through the same choke.

Kick's has some good performing chokes for waterfowl applications. If you can get your hands on some of the heavier-than-lead shells, they may help reach out to those tall geese. They hit you hard in the wallet, but it's nice to have 2-3 boxes just in case.