Our barnyard needs some new fencing. The old one is failing mostly because it's old but the posts are leaning outward quite a bit. In trying to figure out why, I discovered that the previous owner had not sunk the posts deep enough (we need to go about 4 feet up here in Wisconsin). Doing some diging, I discovered why. This part of our land sits on some rock ledge that is about 2-3 feet down. I need a method of setting posts that will keep them stable even in a hole that is not as deep as it should be. Any ideas? Thanks.