Just ran across this on some specific hardware. TC64 and the native Xfbdev *should* default to your native video resolution, but sometimes it does not and you are stuck at a default 1024x768.
Of course, since xvesa can't be compiled for 64 bit, don't go down that path.
The simplest solution here is to just force your resolution manually, by adding a separate line to your grub.cfg file.
Here I added my own resolution and color depth to each menu item in grub.cfg:
.
.
.
set gfxpayload=1920x1080x24
}
If you have a large monitor, and are using the standard fltk utils, those might be smaller than you are used to, but things like terminals, fonts and so forth will be normal in other programs (provided you have actually loaded fonts, changed their sizes and so forth)