If you can control the input of water, I would go 6 inches for opener and then 12 to 18 inches after that. Also you'll need to get use to getting as much movement in your spread as you can especially when its dead calm, in the timber that was easy and inexpensive ( stir water up with foot...lol ). In the fields not so easy, as many eyes will be on you. You just cant move, you'll need to buy or fab something to give your spread some movement. As the season goes the more scrutiny your setup will get, be prepaired to change things up (...ie...more decoys, less decoys, big group, several small groups). At one time or another durring the season, we have as many as 10 dz decoys out or as few as 10 decoys. Hope some of that helps you out.