This may or may not help, but, if you go into Applications-->System Tools-->Nvidia Display settings and can set up the devices, when you go into Save Configuration it will ask if you want to see a preview. If you click on preview, it shows what it thinks xorg.conf should look like. You might be able to get the info you need there.
While I haven't tried your particular situation, it has given me some interesting results with other setups.
Registered Linux User #348347
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Running Fedora 17/18/19, siduction and openSUSE Tumbleweed with KDE