I have an older gasser RV with the usual smallish TV-zone up front. I have already swapped the old crt TV for a 22" LCD, but I want a BIGGER TV, of course. My problem is not the mount, I can weld that. Finding the location of the aluminum roof ribs was a problem until I happened to be standing on my stick and brick house roof early one morning and noticed the the dew on the RV's roof had settled all over the roof, but much less above each metal rib. I could see the layout of the whole roof structure and front two side-to-side ribs perfectly. I didn't start my latest project then, but have filed this info for future use.
My RV just happens to be parked close-by, but the effect would still be visible elsewhere.
A mount would have to be quite stout, even with a very light LED TV/mount combo, since the usual travel shaking could degrade the fastening without much warning unless it was welded. So I am considering changing the mount location to behind the current TV location, up above the cabinets. I could REALLY secure it there, since it wouldn't be as visible. I'd just put a gentle bend in the mount arm.