So to give a better idea as to what I'm going for... I want the mount the articulating arm fairly close to the edge of this cabnet with the arm extending to the right of the picture/towards the wall, on the panel facing the rear of the trailer (the TV will be centered on the wall most of the time, about the same hight as the window, nearby). That way when were in back/in bed we can watch a movie... but the arm will swing around 180-degrees and allow me to point the TV up towards the kitchen/gaucho area when necessary.
This is an early 70's trailer and the cabinet wall is a very leightweight, thin piece of material. I was going to use pass-though hardware to mount a heavier piece of plywood inside the cabinet (out of sight). Then put some L-shaped brackets on it near the interior wall (door-side, in the cabinet).
Finally... attach the L-shaped brackets to the interior wall (still in the cabinet). My initial thought was some higher-quality drywall anchors... but thought I'd check first to see if there was better, or Airstream dedicated/recommended, hardware to use when mounting to the interior wall.