Cygwin X-Free not installed in mounted root directory

[dunkel@ScienceSoft.net]

Following the Cygwin X-Free86 installation instructions gives me a 300
MB installation directory. But everything works -- great job! With less
free disk space available, I removed programming support, fonts I'd
never use, and most documentation to get down to a working 40 MB
installation. I put the software in a separate directory and mounted it
as the cygwin root (mount -b L:/myDir/cygwin /). Works, but I have a
reason to keep the cygwin root directory set to L:/ while installing and
running the software from L:/myDir/cygwin. I need help to get this to
work (or am I just too greedy?).

Now the mount command reports "\cygwindrive\l on / type user (binmode)"
and the startxwin.bat contains "SET CYGWIN_ROOT=L:\myDir\cygwin". The
bash shell works, but when I start startxwin.bat, it reports "Couldn't
open RGB_DB '/usr/X11R6/lib/X11/rgb'" or font "fixed" not found. Is
there a shell variable, undocumented XWin command line option, or any
other magic to tell XWin what the root directory of my /usr directory
tree is where it can find rgb.txt and the "fonts" directory?
(CYGWIN_ROOT does not seem to do the trick and I don't want to change my
root directory mount.) Any help would be greatly appreciated!

ThanX,
Reinhard