I have no exhausted vga mode numbers (decimal or hex), but everything
ends up 640x480 so far. Setting vga=ask, did not display known modes
and piping dmesg into less, there didn't appear to be anything in the
kernel buffer about this.
I can start an xterm that is 70x20. But if I run the CLI installer
from that small window, it still makes new windows which are too big,
and I can't see or work the buttons. I have tried to put COLUMNS=70
LINES=20 GEOMETRY="70x20+30+30" in the environment, and that doesn't
seem to do anything either.