Lonni: your approach may have worked if the EDID data from the working display was actually applicable to the Sony DFP, which it wasn't. [Edit: that is, the control panel still thinks the Viewsonic DFP is attached even when I switch to the Sony...]
The good news first:
I finally got this thing working the way it should.
The bad news is that it took more than software to do it.
I bought a device from monoprice called DVI Doctor - Powered EDID Problem Solver
This thing was very easy to setup. You plug the TV (or monitor) into the device and apply power. It then learns the EDID info from the display. Then you remove power and plug its other port into the computer (it will get power from the computer form this point on). It passes the display data through, but when the computer tries to read EDID data, the device sends what it previously learned from the display right to the computer.
Now the Nvidia driver gets all the correct EDID information and "nvidia-auto-select" generates the correct modeline without any parameters in the Xorg.conf (I'm still hard coding the DPI to 100x100, but that's because of a MythTV requirement).
I've attached a "bug report" showing the working setup. Interestingly, the driver sees the display as "dual link" now...
Now that I've spent $55 on this nifty gizmo, I'm sure the next driver release will fix the problem.