I have not found length to be a problem yet but I can see how it could be a problem.
what I have found so far:
1. The entrance apron is too steep and the rear over hang drags entering the site.
2. The site itself is not level enough.
3. Overgrown vegetation. I have found state park managers with issues trimming trees that scrape my roof and sidewalls.
They advertise and charge for an rv site and ask 'how many feet long you are" but the entrance to the sites are often only wide or tall enough to fit cars.
I am not possibly damaging and scraping my rv on tree branches and shrubs, I have asked at the park offices that their advertised rv sites are too size restrictive. They usually send someone with a pole trimmer to cut branches back.
UV over time makes roof vents and skylights too brittle to play games with even thin low tree branches.