If I'm going to grid an area, I never use an area larger than 10X10. One of the reasons I do that is that no matter what type of hunting you're doing, you have to be focused, or you'll miss signals. It's much easier to concentrate on a smaller area. If you find your technique getting sloppy, quit for the day and hit it again some other time. Also make sure your grids over-lap, targets can be missed if you only hunt defined lines. I use natural materials to mark the grids. Don't move things around and make nice squares. If the area is that good that you're gridding in the first place, don't advertise it for someone with a sharp eye. Most people will see all those filled in holes and go look for somewhere else to swing that hasn't been pounded.