Can you get a pop-up on a 20' site in Yellowstone? We tow with a mini-van if that matters. Our pup is a 10' box so a little less than 20' deployed. But in most campgrounds you gain more room over the rear stop of the site. I've read some places (here?) that people have done it, but we just called and they told us we'd need a 30' site... which are pretty much gone for our time frame already. Is this accurate?