You don't want to change ther servos any, and you don't need to "slow" them down. Also, you don't want to change the end points either. Adjustments made in a computer radio should be made ONLY after all mechanical adjustments are made on a plane. Many times people will try to make adjustments with a computer radio without having the plane setup correctly first, and wind up making things worse or even dangerous to the point they can endanger the plane. Instead, you need to reduce the amount of throw (distance of travel) on each control surface. By lowering the throw you will change how sensitive they in the situation you described.

Ken