If I'm using standard size decoys on open water they're always spaced no more than 4 feet Normally a 3 decoy wide oval. My reasoning is that it creates a big dark spot at a distance to get attention and when they get close it looks like the decoys found good feed. Honestly I never spread out standard decoys much because everyone else does. 5-6 is maximum on smaller water. Be different. I space magnums about 4-8 feet, lets the big decoys work their magic.