[jsb5717]

Length and width are both issues to pay attention to. A lot of State Parks in Oregon were built long before RV's had slides so trees also come in to play. Also, there is a huge variable in site layout that might provide ample room to hang the trailer tail over the end of the site. Basically you can often hang 10' over so a little shorter site will still work. Then there's the need for enough room for your truck as well.

With a 35' trailers I do my best to check those elements with available pics or Google Earth. Many private parks don't offer site pictures or even allow you to select your own site so you have to leave it up to them to place you. There are a lot of sites in State and County parks that are too small for us. But we've always managed to find adequate space. For me I wouldn't worry about having a trailer up to 37-38'. YMMV