I know that a TH2G works on the GT120 - not tested 2 x dual heads...

When I tried it with a TH2G on the minidisplay port - max res I got was 2400x600 on both outputs.

However, you should think about how you are running your control screen - if its on the same head as a projector - both projector and control screen would switch back to desktop and full screen. If you use a TH2G, then you can isolate control from the projector outputs - this means that if you switch back to desktop on your control screen, your projectors can remain in 'full screen' on the the output.

Whatever you do - test it....

Simon