I use 2 dozen Real Geese along with 2 dozen standard shells, 18 magnum shells and 12 persuaders for canadas. They seem to work in conjunction with the shells and add the illusion of movement as the geese fly over or so the articles say.
Silos work well just remember to set up at different angles. We shoot a spread of 4-6 dozen silos and 2-3 shells and have no problem with honkers & specks. I use Outlaws - buy them after season for the best prices.
I should of wrote they made a positive difference. As far as realism, in my opinion they look good in the field. Once you lay a bunch out you will see how much better your spread looks. I tied some up as windsocks which work great, but very boring to rig and the others as texas rags. next trip I will get a photo and post it.