go ahead and cut your shells to 2 1/2", buy some 16 ga over shot cards from Balistic Products or wherever you can find them. Put one in on top of your shot and run the shells through your press, without adjusting the shell height on the crimp station. You should get a normal crimp, but the center will be missing. The card keeps the shot in place. I and others have been doing this for years.

This ain't a dress rehearsal , Don't Let the Old Man IN