XFree86 and Composite Video for a fixed freq monitor

[turbo__]

I happened to stumble over a Sun fixed frequency monitor (GDM-1962b). I have found a number of modelines availabe for the monitor that partially sync the picture, however without a composite signal the picture will not completely sync. In windows, their is a composite option available in the ati display properties. I can't seem to figure out how to get composite working in X though.
My setup:
RH 7.2 default install
Video card: ati radeon using the ati module in XFree86Config
I would appreciate any tips provided.