I found this Optimization and Improving FPS Steam Guide which helped me get some more FPS out of Arma. I used to run Arma around 30-ish FPS, but now I am in the range of 30-40 which is quite an improvement. For sure worth checking out.
The guide have information about the startup parameters as well as some explanations to some of the in-game settings which I didn't have no clue about until I read this guide.
22nd [SAS] Elite Virtual Regiment