Wondering if you installed your fence yet. I'am about to do the same, for the first time. I've figured that the posts, 4x4 pressure treated need to be spaced every 7'10" to carry the next section of fence.( 6x8 sections) The posts are a standard 8 feet and I'am guessing 2-3 feet would be posted in cement. Has any one seen a plastic spike type support, approx. 3'feet that can be hammered into the ground, with a 4"x4" setting for the post? Can this be used? Or, should I just cement the posts?