I found another place where you can sail from your RV: Floras Lake on the coast in southern Oregon. This is definitely not a destination for windsurfing, but if you're traveling along the Oregon coast, you'll go right by it. That's what we were doing, and good wind was predicted, so we stopped there.
It's kind of a cool little (and I mean little) lake--on the far side of the lake, you can walk over the dunes to the ocean. Some of the kiters were over on the ocean side; we went and stood in the water over there just to say we did, and it had those scary sneaker waves so we scurried back to the lake.
There's a state park on the southern side of the lake, but the windsurfing takes place on the northern side; the prevailing winds are northwest. And these winds make it kind of chilly even in June--a full wetsuit was definitely the call. We coped by telling ourselves it was the nicest winter sailing day ever, and were easily fooled because we hadn't seen even 80 degrees since last October.
After the sun got low, it got downright cold--people sitting around outside were wearing jackets.
There's a
windsurfing/kiting concession there. It's adjacent to Boice Cope County Park, which is where we stayed--a no hookup campground with a dump station, for $16/night. Pay showers. Almost everybody there was either kiting or windsurfing.

To get to the water from the campground, you go down a path through the trees. I think it could be tricky to carry rigged equipment down there, but there's room to rig at the bottom and several people left their rigged sails down there overnight.
It's allegedly a shallow lake, but of course I found all kinds of deep spots. It also allegedly has relatively smooth water, but I don't know because the wind never picked up like predicted. It turned into a day to putt around, with a couple of decent rides--mainly a good reminder that we still know how to do this after a year off, and a nice break from the constant touristing over the previous week.
If there were real wind, it would be an excellent place to practice one's jibes because the reach is so short. This is almost the whole lake:

The ocean is on the other side of the dunes:

I don't think anybody would ever plan a trip here (one guy asked how I even knew it existed), but if you tour the Oregon coast, it's less than a 3-mile detour off Highway 101.
If you have a hankering for waves, south of there, in Gold Beach, is where they have the Pistol River Wave Bash (which we missed by just a few days).