I d be havin a tin fence to max height ,6'6" tall here,with the wire rope behind it....tin fence so no one can see in......the idea of the wire rope ,is if its hit ,the pull ends up on all the posts ,not just one,so they dont need to be all that big to stop a car.........If you look around ,most places you can get used wire rope scrap price ,or less....cause its not popular with the scrapyards.I would have three strands of wire rope,same levels as plain wire horse fence........gravel is nice,but is kinda dear here.....like $1000 for a 10 ton load.