v6 has canvas zooming but it's not great(
a lot of visual bugs) so your options are pretty slim. What you can do is resize GraalControl and try adding ChatBar to GUIContainer, which should make it visible all the time. Then if the black is ugly try filling it with some graphics like the ol' Super Gameboy(since gameboy resolution didn't match the output resolution of the SNES):
Be
very careful tinkering around with default controls. I mean, you're not going to say... crash a client but they're not scripted with being tinkered in mind. You'll have to account for the various things that can throw it off and mess everything up, like a new GUI being added to GUIContainer or such and not being accounted for on your end.