I got the "behind the wall" plans from Jayco in a PDF... had all of the specs and measurements.
What is behind your wall? In ours it's the bathroom, and that wall is 3" thick. There is a piece of 3/4" plywood as a backer attached to the studs, to make a sturdy mount for the TV.
All told, it gave me about 2 1/2" of space for the screws. So what I did was put a bead of silicone sealer on the back of the mount, and then secured it with 2" deck screws (no pilot holes required).
So far, all is good!