After several times fooling around with YDL to get a decent color
palette at 800x600 on the 6360 (also a Umax C500, both of which seem
to use the Valkyrie chip for video) I got a clean 800x 600 desktop
(with one known caveat).

In MacOS set your monitor to 800x600 60hz, thousands of colors.
Install Linux via booxX have force video settings and no video drivers
checked, etc. Go through the install. Let Linux pick the generic OF
Video and let it assume 640x480/thousands of colors. You can pick a
monitor if you want.

Afdter install leave the video checkbox setings on BootX as they are
and don't mess with the Display preferences via the X desktop (once
you fiddle with them your color palette takes a dive.).

The Caveat I've found is under Gnome the screen saver is still
thinking 640x480 and does not completely cover the screen. On KDE the
full screensaver is working though flipping through the different
savers choked the saver somehow, (not sure it it was the slow computer
or the mismatch in perceived resolutions.)

So it can do it, it's just that LinuxPPC is missing the Valkyrie
drivers or they are not completely right yet. Until there is a real
answer to the video settings at least it makes the GUI more
acceptible.