We have been to Cass, I would guess that you are going for the same reason I had wanted to for years. It seems you have a F250 and a 26'TT. How are you at driving goat paths?
If you try to approach Cass from 219, that is Cass Rd. (66) and it is 12 miles of twisty windy roads that would remind you of New England.
If you elect to approach from 250, you will want to break south at Bartow for Patomac Highlands Trail (92-iirc) and that will take you though Green Bank. There are signs that instruct you to shut down your cell phone because you will be in the shadow of the radio observatory. Look west in Green Bank and you should see the dish. Just after that you should be able to break west. I recall a sign there that says you can join Cass Rd (66) there. When you get close to Cass, there is huge parking lot on the north side of the road.
There is a campground not far, but we didn't find it. We were out of season and didn't even look real hard. We rarely use regular campgrounds.
We had a great time there because we were out of season and being a steam engineer, I did what I often do which is look for the "Authorized Persons Only" sign because that is where I want to be. We got to the engine shop and when they found out I was a steam engineer, it was like meeting old friends. I would doubt that you can do that.
You wrote one time that you are not big on the blue roads. If I remember that right, you will love this. The trucks you meet coming the other way will understand.
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.