Are you talking about studs in the outside walls?
Forester framing is aluminum tubing. A magnetic stud finder won't sense them.
There is no regular spacing. They are placed wherever they are needed such as around windows, slides and doors.
I've seen the framing outlined on our Sunseeker. When it's cold and humid, and the coach is heated, the heat loss through the framing prevents condensation on the outside walls.
2011 Sunseeker 3100
1997 Pathfinder Toad