The first 5th wheel of any type I drove was a friend's 44' toy hauler. Drove it through Flagstaff and then south to Tucson. Towed very nicely and I didn't have any trouble getting used to it. My first 5th wheel was a 37' Everest that we towed all over the country with no problems. I even pulled it through a WalMart parking lot, through the aisles, and up to the front door - it was easy. My current toy hauler measures 41'. It's new but so far there haven't been any issues towing it around.
I haven't found anywhere on our cross country trips that we couldn't go due to length or height. When it comes to trip planning I figure if the 18 wheeler's can go there, so can I. If I will be on the back-roads I check the truckers road atlas to ensure it's a truck route.