Well, color me red and call me stupid! That was way too obvious & easy... I added this :
ModulePath "/usr/X11R6/lib/modules, /usr/lib/xorg/modules/extensions/nvidia, /usr/lib/xorg/modules"
This time it couldn't find the module nvidia, which appears to be in... /etc/modprobe.d. Unless that's not the file I'm looking for (as eyes glaze over...)
Slowly getting there...
My X log file tells me the nvidia module is in:
/usr/X11R6/lib64/modules/drivers/nvidia_drv.so
Again I'm assuming you would have to replace lib64 with lib.
Michael