I find that Washington State Parks are pretty generous space wise. Over 32' are usually huge sites. The problem you will encounter is the roads in some of the campgrounds. Deception Pass SP is very nice but the roads in the park are tight with a lot of large trees right next to the road with sharp turns. A large 5th wheel can navigate tight roads better than a bumper pull in my opinion. Washington does list a few parks where large RVs are not permitted. If you stick to and 5th wheel under 32' you will be able to get into almost any State Park: I've been able to get into any park I want so far.