well if you are only getting 45fps, turning on vsync is not going to fix stuttering.
45 fps on a single gpu setup is plenty smooth. 45 fps on a 3 way gpu setup has little tiny mostly unnoticeable hiccups to anybody but only the the most discerning eyes. I happen to have a set of those eyes. Vsync cleans it up some but still is barely there. I suggest you read up on the issue more before you come in here and tell me what is and is not gonna help.
I have come from
6600 gt sli setup
7800 gt sli setup
8800 gts 320 sli setup
8800 gt sli setup
9600 gt sli setup
and now my current 4870 x2 and 4870 1 gig crossfire setup.
I know the ins and outs of multi gpu better than most people.
The point I was trying to make in my first post was that If Hydra is using a different type of multigpu other than AFR(which is almost the sole cause of microstuttering), there is potential to avoid said problem. Making 45 fps as smooth using multigpu as it is on a single gpu.