SLI is very bad for arma 3, atleast for me:
2016-02-01 18:58:13 - arma3 GTX 760 2 waySLI
Frames: 8390 - Time: 109640ms - Avg: 76.523 - Min: 45 - Max: 120
2016-02-01 19:02:52 - arma3 GTX 760
Frames: 7941 - Time: 109235ms - Avg: 72.696 - Min: 41 - Max: 109
2016-02-01 19:08:10 - arma3 GTX 760 2 way SLI
Frames: 8103 - Time: 109266ms - Avg: 74.158 - Min: 33 - Max: 123
2016-02-01 19:12:48 - arma3 GTX 760
Frames: 7782 - Time: 109500ms - Avg: 71.068 - Min: 42 - Max: 110
Btw settings are something High-Very high