Why do I get more FPS in ARMA III with 1 card OC'ed then 2 OC'ed?

[kaio37k]

I recently benchmarked my new 660 Ti SLI setup in ARMA III and found that when I had one card I was getting 60FPS on Ultra, but with the same OC with TWO cards I only get 29FPS... Whats up with this?

 

[Cons29]

poor support for sli maybe