Our 5er is 40' long and only had a problem once. Last year at a COE in Georgia we were able to get in our campsite but ended up having to back out of the loop. The turn around area was very tight with trees on outside and some trees on inside. Park attendant said some people had made it, some didn't and a few almost got stuck. He said a lot backed out, so we did, no big problem as the road was wide so it was easy to do.
As others have said, just have to watch when turning as it does take a long swing sometimes. Don't see us going to a smaller rig, maybe longer next time.