Jay,
The t-6 crossing is a 14 mile hike south on the Pacific crest trail from the hot springs. Or you can get there from the tiny neighborhood of Cedar Glenn just off hwy 173 at the end of hook creek rd. It is a cement bridge built to protect the endangered frogs there from 4+4 tourist.
The rule is you cannot be nude with in 1/2 mile of the cement bridge there.
Also the supreme court recconised in the 70' that nude recreation was a free speech right in our national heritage the forest.
Glad to help !