My coach has a 27" CRT TV above the dash, sitting is a cabinet.If I purchase a 28" HDTV, it will fit inside the cabinet, with room to spare. If I purchase a 32" HDTV, it will fit flush on the outside,...
I think most folks go with what sch911 is describing using a piano hinge so you get access to the storage behind it. Other folks use articulating arms and mount it to the inside of the cabinet. The issue is keeping it from moving while in transit. There are several examples of installations in this RV tv installation article.