It should be possible to do this with the Adrenalin software...
If I'm sending video to just the 4K TV, I can use 3808x2142 instead of 3840x2160 to accommodate the viewing angle being crap along the edges of the screen, and tell the TV to center the image so that there is a thin black border in the parts with poor viewing angle, so it doesn't look like there is a letter or so cut off along the edge.
But if the display is cloned it doesn't let me do this. If not through an explicit custom resolution, something like this should at least be doable as "underscan" .... which brings a separate question of why the underscan adjustment is also available (through Adrenalin) on an attached computer monitor but not on the TV.
