The actual "ideal" rotation for maximum line length would be closer to 23° rather than 22°, right? Because Atan(9/21) = 23.20°.
Also... could we go further? If we're treating the screen's content as an arbitrary plane, what about tilting the content of screen away from you like SNES Mode 7 or the Star Wars text crawl? Infinite screen height!
Does character height affect that calculation? The longest line possible wont be able to render at the ends, so is it possible there is a shorter line on a different angle that can render more text?
Also... could we go further? If we're treating the screen's content as an arbitrary plane, what about tilting the content of screen away from you like SNES Mode 7 or the Star Wars text crawl? Infinite screen height!