On Redhat 7.1, my previous distribution, the XF86Config had dozens of modelines which i was able to add to to acheive the resolution i wanted.
In Redhat 9, the file has been cleaned up substantially, and it seems modelines do not belong in there any more...anyone know if they can still be used, and where? I've got a perfectly working modeline here and nowhere to put it...

Ok, I never worked with modlines (shame on me ;-(
But I found a way that works also:

When using the configurator redhat-config-xfree86
you usualy see that you are limited to a resolution of 800x600 or something and wonder why you cannot select something bigger.
The thing that I learned now is that the config-tool does not recognize your monitor correctly, therefore it puts really low horizontal and vertial values into the monitor settings.
Try this:
depending on your monitor, go and just edit these values, punching up the horizontal values. That should give you a higher resolution (I guess that is was you need, right?), but careful, don't go too high or you might fry your moni. The range usualy says 30 to 40 or something and that is very conservative, i.e. does not give you any great resolution. Most monitors can handle 60. If you got a new one, (>3 years old), if might eat up to 80khz.

When done, you can choose a higher resolution for it.

I'm not sure if I am answering your question or one that was not being asked ;-)

If you think the tool that I mentioned will help you solve the problem, try it out or post what monitor you have and how old it is and I probably will be able to tell you how high you can punch it (no warrantees though)

Cheers

Markus

thanks markus i'll give that a try