Sli needs at least 3 prerendered frames for frame delivery stability, as you will otherwise see massive stuttering from the spikes in frametines on the cpu.
This is the only game that lets you overwrite the otherwise driverforced 3 prerendered frames for sli, and it does technically function, but performance is atrocious with only 1 prerendered frame with sli.
But bottomline is - if you have used sli in any other game, you will have used the equivelant to future frame rendering enabled.
A way to get around the input lag, is setting g-sync correctly up - it will drastically reduce your input lag 