I've got what I'd call an average or a bit smaller TV. When we play split screen, I have to go up very close to be able to read any text. I don't think there's any way to change it.
Split screen can be very difficult on certain maps and game modes because the top and bottom of the display are cut off a bit. Sniping is a pain, and it's hard to see objective markers and the icons for enemy spawns.. I find moon base z particularly tricky on split screen.
If you find a way to change it, please do post again.
@asukojo, you play split screen quite a bit. Anything to add?