I took a look at some other Unreal Engine games to see what they did to get SLI working. The following worked for me:
In Nvidia Inspector use 0x0080000F5 for SLI compatibility bits (DX10 + DX11) and then use AFR2.
There are some flickering issues with SLI in the UI menus, but nothing I've noticed in the game itself.
Would be awesome to have official multi-GPU support.
