Prerequisites for making an OpenGL app SLI compatible?

I’m in the dark. I’ve scoured the web but can’t find any specific guidelines on what’s required to ensure SLI compatibility - though lots of documentation about how to best optimize for it once it’s enabled.

Although it isn’t OpenGL specific, I’d also really like to know if SLI is capable of splitting the work of fragment shaders ala the fullscreen quad / fragment shader approach.

General information would be appreciated but I also have some app specific woes -

Our app centers around a GLSL fragment shader which draws cumulatively to the backbuffer for a set amount of iterations. As I understand it, this means Alternate Frame Rendering is not the best option as each frame relies on the result of the previous frame. (Though I’m willing to come up with a creative solution, if it’s the only way). I know that the Split Frame Rendering SLI mode was previously an option in the Nvidia Control Panel - this seems a more fitting / versatile solution to the problem, though I’ve had trouble implementing it - by forcing the mode with a 3rd party program, along with the SLI indicator enabled, I notice that both my GPUs are in use, though the render time remains the same, making me think they’re simply sharing a copy of the backbuffer and doing identical work. The indicator was drawing to the buffer being sampled and becoming a part of my renders, which prompted me to do a little more reading.

Though I could find a little documentation regarding Split Frame Rendering, it was mainly concerned with operations we’re not making use of in this app (no mention of fragment shaders at all), but seeing as our render times would decrease dramatically if we were capable of utilizing multiple cards, we could really use the extra horsepower - any tips on how to set up our code to make use of it would be greatly appreciated.

There’s the option to simply split work between frames, switching between them and combining them later, though this would require some convoluted code and would break non multi-gpu setups without user intervention, so I’m hoping that SFR is still supported in some manner in the current drivers, even if nvinspector is the only way to enable the mode.