I recently replaced the tube TV in my coach with a Sony 24" Google TV. I wanted an internet ready TV and this is only one I found that would fit without mods to front cabinet doors. The old TV removal was simple, as it was held in by 4 corner brackets easily removed once trim was off. The box was framed in wood, not metal.
I used a 2x6 to make the support for TV mounting bracket, I used a swivel type mount.
I trimmed both sides of box opening with foam weatherstripping for the TV to rest against. I attached 2 D ring picture hangers to back of TV using screws from mount, and placed 3 small bungies on each side. I then inserted an eye screw in rear of box on each side to for bungee attachment, to keep the TV firmly snugged up against the box frame.
Due to the fact that the TV had a curved back, I was concerned that if I hit a hard bump the TV could slide and be pulled by bungees into box, so I made backstops out of angle bracket, covered with foam weatherstripping to prevent this. After reposistioning, the TV rests nicely on these.
This is what the TV looks like snugged up against the frame, with no covering on the rest of the opening. Plenty of space to unhook the bungees to bring TV forward if needed.
I then used some angle brackets to make a support for the foam I used to enclose the remainder of the opening. I used 2 large ones on bottom, and 2 small ones on each side, set 1" back.
I used baby bumper foam pieces cut to appropriate length. They are 1" thick and nicely rigid, I covered this piece in black speaker cloth and inserted into space.
I will probably get a small surround sound system eventually, plenty of space in box for small woofer, and could use the two speaker boxes on outside of front cabinets for other speakers. Right now the sound from TV is not bad, even with bottom mounted speakers. The sound got better once foam was placed in bottom opening. If I get "bungie fatigue" too soon, I may replace them with springs, but the bungies sure are simple and hold the TV nice and firm.
Thanks for all who have posted about TV installs, I used a lot of your ideas.