The key is to scope out parks before you arrive. We don't have a 42 footer but we still look for parks with good access. We use www.woodalls.com and they have a "big rig" search function. Once we decide on a couple of options, we look them up on www.rvparkreviews.com to choose. I look at their website to see what they say about their sites (pull thus etc) Then I look up the address on google maps earth view and zoom to see the entry and access. Many sites like www.recreation.gov and www.reserveamerica.com show the sites and lengths. We have been all over the US and into Canada (not Alaska in our current DP) and have never had a problem finding sites. We did rent a Class C in Alaska and found many parks that had sites that could easily fit a 42 footer. We also used Milepost for the Alaska trip.