Do the interior walls have wood or metal framing. If wood you might look close and find vertical rows of thin gage staples where the paneling is stapled to the studs. An electronic stud finder is also useful. It senses the difference density of the wall with a row of LEDs lighting up to indicate the studs under the paneling. The walls feel soft becuse they are only made using 1 inch thick studs and thin paneling on each side with no filler material between the studs. Depending on the wall location and support needed the studs vary in width.
I used an electronic stud finder and spotting the staples to locate the wood studs. The stud finder also allowed me to determine the width of the wall studs. It also helped me to determine there was a piece of plywood between studs where the 2 tv shelves were located that the shelf brackets were attached to.
I lowered the shelf on the wall between the dinette and bunk house about 2 to 3 inches allowing me to place a DVD player and satellite receiver on the shelf and still be able to open the cabinet door next to the shelf. I found the edge of the wall had a 1x3 and allowed me to drill through it and mount a narrow based articulating mount using 2 bolts, 2 fender washers and 2 lock nuts. The normal position for the 21 inch flat panel tv was against the wall above the DVD player and satellite receiver. I can swing the tv around the end of the wall to face the bunkhouse and also have full access to the cabinet.
I used an identical tv mount, bolts fender washers and nuts for another 21 inch and later a 29 inch flat panel in the bedroom. I drilled through a 2-1/2 inch wide stud I located in the wall and mounted it with the fender washers and lock nuts on the living room side of the wall. I repurposed the bedroom tv shelf since it was too low and in a corner blocking me from scooting around the bed to use as a counter extension in the galley. The formica top was an exact match for the kitchen counter.