I installed a heavy articulating TV mount for my 24 inch TV. The TV is super light, but the mount is very heavy and came with the huge long screws.
I am sorry my measurements are vague at this point, but at the time I was measuring and scheming until I figured it out. Now those exact sizes are forgotten. If you have trouble following my diagram description, let me know.
My little old rig (1994 Class C) simply has a small folding table in the wall to hold a TV and warned you to NOT keep the TV there while driving... duh... I did put my new 24" TV on it to watch, but I wanted the TV permanently mounted so I could drive without having to stow the TV every time.
Anyhow I was able to remove the built-in folding table to look inside the wall. There was a stud to the right of the table that wasn't nearly thick enough to hold the screws, but the wall had room enough. For instance the wall was 3-4 inches thick, but the stud was only about an inch or so thick, it didn't reach between the bedroom panel to the bathroom panel. Very strange. I guess it just supported the bedroom side of the wall.
In my case this was the wall between the bathroom and bedroom. I used a section of 2x4 (that happened to be a perfect fit) I found in a scrap heap out of sheer luck. It looked like it had been cut to perfectly do the job.
I did measure to see how the TV would fit on this stud, since the mount was a heavy duty articulating type, the TV can be adjusted multiple ways for viewing. So this convenient stud to the right of the folding table was going to work size wise for the 24" TV. I was thrilled to discover how all this was falling into place.
Anyhow I jammed the new chunk of wood between the bathroom wall and the small (floor to ceiling) stud. This now gave me a huge chunk of wood to put all the big heavy long screws to hold the mount. I guess you could say I was using the spare hunk of wood as a backing plate.
Before I mounted the TV, I did play with the articulating mount a good bit, jumping up and down, trying to wiggle it and so on. It seemed very firm refusing to budge. I replaced the folding table back in the wall to fill in the big hole to the left of the TV even though I don't need the table, I surely didn't want the empty hole either.
Seems you could cut a nice neat rectangular hole in the wall to do the same, (Look and see what's in that wall and insert your own lumber etc.) then put up trim pieces of molding and screw the wall piece back in, much like a shower access plate.
I mounted the TV which is very light once the heavy glass base table top base it came with was removed. I've been using it 7 months now. It's gone bouncing the highway and some rough roads with me now and over the mountains. When I get ready to travel, I put the articulating mount and TV back flat against the wall and tighten the knobs. For good measure, there is a long heavy ribbon tied to the mount. I tie the ribbon up like a bow around the TV top to bottom (vertically) to make sure the TV can't move around even if the knobs vibrated loose (they never have).
I didn't want to use a bungee cord around the TV as I worried it might distort the LED screen resolution. The big wide ribbon happened to be laying around as this was at Christmas (it came wrapped around a gift) and it seemed like the perfect size for the job.
Every time I park to set up camp, there's my Christmas TV with a big bow tied around it, ready to unwrap again.
I must admit the articulating mount is WONDERFUL. I sometimes pile up the pillows to convert the bed to a couch or lounger, then watch TV. I can angle it perfectly for that. Then I can also adjust the TV for perfect viewing for laying down as well. I can bring it out from the wall to twist it at an angle.