...no clue what that means...
Ok... here's how I just got it working.
Main guide & inspiration:
http://www.xbox-linux.org/wiki/Xbox_HDTV_HOWTO#X11
With my Classic XBox (Xebian Linux) and 32" Sova TV...
(1) Got FBSet code working in /etc/fb.modes (executable via fbset 720p)
<See code window below>
(2) Found
http://www.arachnoid.com/modelines/ <-- This is what I needed as an answer to my question
(3) Played with the modeline in multiples of 8 for the values shown below of 1384 1648 and 1698 in /etc/X11/XF86Config-4 until I reached the proper horizontal fit...
Modeline "720p" 1280 1384 1648 1698 720 723 738 750 -hsync -vsync