Need Advice for Backing in 41' Long TT to Camp Site

Practice backing in an empty parking lot until you get it down. Take some orange cones, or even a few blocks of wood and lay out the parking like identical to your campsite. Then practice backing in, in the space you've marked out. No one watching, no one to critique you, nothing to hit, and at the most, a tire will run over a 2x4 on the asphalt. And then you'll figure it out.