I don't know the answer to your question. However, we had the factory install one of their customized cantilevered Omni mounts on the outside wall of our trailer last year.
First, they installed a wood box about 12" wide by 18" high on the wall that is tapered from being smaller at the top to larger at the bottom, to compensate for the rounded sidewall of the trailer, so the Omni mount is vertical when affixed to it. The box itself is hollow inside, so the wires from the TV run down inside it out of sight.
I didn't see how the wood box is affixed to the wall, but Airstream put a customized metal back plate on top of the wood box that has a total of 10 screws in it, plus the 2 large lag bolts in the Omni mount itself.
As I recall, Airstream charged us about $200 for the entire mounting system, including labor. I bought a Sharp flat screen TV on Ebay for less than I could have gotten one locally, we have Dish 500 with umpteen hundred channels, plus local channels from Denver when we spend the summer in Montana, and we're very happy with the overall product.