I'd like to know what is the standard height for metal clothes line posts. I have 2 nice galvanized 6'10" T-posts. Don't want the posts to later sag toward the middle. Excavated square holes about 20" x 20", 16" deep. Figure top of posts need to be about 5'6" to 5'10". Wonder if should hammer rebar into ground, slide post onto it, concrete it. Any thoughts welcome. Thanks.