And, I have no idea how to determine if it's a proper NTSC modeline. Those modelines I post were generated via the command:
I ran that command from a terminal that was in black and white because it was running off the component cable.
I also ran that command, on the same physical monitor, on X screens that were hooked up to a D-SUB cable as well as on an Xscreen that was hooked up to a DVI cable. All three gave the exact same modeline.
Maybe they were all the same because they were all run on the same physical monitor? Even though each time gtf was run, the monitor was using a different type of cable that was plugged into the monitor. One time it was DVI, another time it was D-SUB, the third time it was a Component cable.
I hope those last three paragraphs make sense.