I just got the Nvidia 3D vision glasses and I did some experimenting. I couldn't get a GeForce card to work in stereo.

So I installed a Quadro FX 580 (no frame sync connector) and it works with the NVidia 3d Vision setup...

...without using quad buffering!!! Just
Code :
glDrawBuffer(GL_BACK);
Running an application at 120Hz the frames get displayed alternating between left and right eye, just how it should be possible without a Quadro card... Of course you have to check for correct sync and frame performance yourself.
(running in windowed or fullscreen mode)

So this setup comes as close to "manually controlling" OpenGL stereo as possible.
Now we only need to find out how to hack the NVidia drivers...
Setting the window to stereo seems enough to activate the IR transmitter, only problem, on Geforce cards we get "pixelformat with necessary capablitilies not found."

I used GLUT (lazy me) for my testing with:
Code :
glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGBA | GLUT STEREO);

Any comments or ideas?