Been hunting ducks for years. You can have the best looking spread known to man, but if that's not where the ducks want to be your out of luck.
Rule one: ducks always land into the wind. Instead of putting a hole in our spread, we usually place ours in a "C" shape giving them an open invataion to land. Sometimes we will place two seperate spreads which from the air proabably looks like a hole in the middle. The main thing with duck hunting to to scout and find out where they want to be and what direction the wind is coming from. No matter how good of caller you may be if that's not where they want to be, it will be a long day.