Schmick...We usually stay in private RV parks, but not because of the trailer. Most sites in state and federal parks cannot even accommodate a 40' motorhome by itself.
The private RV parks usually have larger sites, easier access, and an overflow area if necessary, for the trailer.
Sometimes we call an RV park ahead of time and make sure they have sites big enough(65'). Other times, we park on the side of a road or in a large parking lot, unload the van and personally check out area RV parks first hand.
We use the GS RV directory too, as it tells the length of sites in each park. So far, the trailer hasn't been a problem and we have a nice clean car and ATV when we get to our destination.