Hey marc515. We just bought a 181 and I want to hang a TV as well. I called the factory yesterday and they told me that the structure is located 9.5 inches from the slide out and 13.75 inches from the slide out. This measurement is on the street side behind the slide out, above the radio/dvd player. As of right now I have not started to hang the TV or look for the structure, but I will let you know when I do. They said that the structure located at these two measurements is 2 inches wide on center of the measurements. I am guessing at this point that the structure is metal studs.
Did you ever get your TV hung? If so, how did it go? Any pictures?
I am going to pull out the micro and see what structure is there or can be added as well.