I have seen a number of sites where there are walls, trees, bushes, etc directly behind the site, so do not count on overhang, you may not be able to. This site in Black Rock Mtn SP in Georgia has a wall made of RR ties and a tree directly behind it. When I stepped out of the trailer I was stepping onto a wall that separated me from the neighbor beside and below me, then I walked the wall to the rear to steps that took me up to the picnic table and fire ring behind me that is a shared area with the site behind me. My buddy got that site.
The site is listed as a 30 ft back in. The truck and trailer together is 44 ft.
Second pic is my motorhome at Cloudland Canyon. Now, I had no issues on length but it has a wall that drops off behind the site and a tree right at the wall, I wanted to get back to the picnic table so I backed all the way up. The site is listed as 50 ft back in, but there is no extra overhang.
Charles