Altering these values in ArmA2.cfg may improve performance slightly:
Lowering mouse smoothing in profile.arma2profile values can reduce mouse lag and may improve FPS slightly:
Higher FOV increases performance, take your FOV values and multiply them both the same. E.g. values 0.75 and 1.20 become 0.975 and 1.56 when multiplied by 1.3. Use to your liking. This does not effect your zoom distances.
This maybe useful regarding hard-drive speeds. To speed up your hard-disk look here