It worked for my trio of 2560×1440 three years ago, not sure if I got it running with Flawless Widescreen, but these things are always finicky and results can vary, some games Flawless Widescreen worked for me others, the Widescreen Fixer did the trick.
The biggest, issues for me were with mods, these fixes are for Vanilla. SkSE and Multi-monitor was always a problem, SkyUI never did work for me, the mods were more important in my case, so I ditched Multi-monitor's, Now the same pair of HD7970's would be crippled. The performance of a single monitor today is approximately what all three managed back then
Wide·Screen Gam·ing Fo·rum (WGSF) these are the goto experts, if you are serious about Multi-monitor, join the forums, and ask them for help