It would depend on whether you're putting your toys in and out at the campsite and the layout of the site. If you need to lower the ramp then you may need more room. At some campsites you couldn't lower your rear door because of the way the site is situated. There is no hard and fast rule.
Also don't forget that the 10 additional feet will only allow you to open the door, then you'll need the room to roll out the toys, which could add even more space. Best thing to do is talk to the hosts in advance and let them know what you have. We often have unloaded our bikes before parking the toyhauler.
Howard and Peggy
"Don't Panic"