Token's Moonshot Build might help describe what size screen you can achieve from a vertical TV mount.
Spoiler: A 42" TV is the equivalent of a 25" 4:3 display whether it is vertically or horizontally displayed
yea after looking into it i found it to be closer to a 26" than is it 25. since a 25" screen is 19.98" wide where as a 27" is 21.58" wide. so that would become the height of the wide screen so in this case a 42" has about a 20.57" tall screen which when rotated becomes the width of a 4:3 screen. me personally i was happy with a 25" so i guess if i go LCD i should aim for a 42"