Jarvis,

The answer is....it depends.

Increasing the amount of side area aft of the CG (such as stab SFGs) will shift the yaw characteristics of the plane to being more stable, more damped, and more likely to yaw into a crosswind (especially in turbulent air), and the amount of rudder input require to generate a given amount of yaw will increase (and drag will increase as well when in the yawed state).

Increasing the amount of side area forward of (or at) the CG will decrease the yaw stability, make the plane more likely to drift with a crosswind, and reduce the amount of rudder input required to generate a given amount of yaw. Of course adding this type of side area will effectively yield more KE power.

I have seen examples where the plane was minimally damped in yaw, and prone to skidding in yaw with any amount of rudder input. In this instance, adding SFGs to the stab both increased yaw damping and increased KE power as the fuse was likely to skid in yaw.

If you don't like the amount of KE power or yaw stability (or the balance between the two), SFGs on the wings / stabs are an effective way to change the balance.