Hi Teresa and Randy,
You are going to love your new Airstream!
From the top of the sofa the bulkhead is 30" wide, and from the top of the window it's 25" wide.
After much shopping around, we installed a Toshiba LCD 22"x16" w/a built-in DVD player. Nice and flat, and fits snugly to the bulkhead when strapped in. Keep in mind the bulkhead is probably 3/4" thick and there's a refrigerator right behind it. We used a wall bracket that came with two holes, and drilled a couple of extra ones for stability, but on hindsight that was probably over-doing it. We got a 2" wide strap with velcro attachments that I trimmed to fit. It's screwed to the bulkhead and carries most of the weight while in transit.
We positioned it so the top of the TV is about 1" higher than the top of the window.
Viewing from the galley is perfect, and very comfy. Have fun!