iTween Shake intensity issues

I am currently calling a Camera Shake using iTween.ShakeRotation . I want it to feel like you are standing on the deck of a ship, slowly swaying back and forth. When I modify the amount and the time I get only one intensity. Extremely violent. Either very fast oscillations (between 5 degrees) or if I pump up the magnitude, I get very fast oscillations between 30 degrees.

It does shake but I can't seem to turn down the intensity. Can anyone assist?

     public float ShakeX;
     public float ShakeY;
     public float ShakeZ;
     public float ShakeTime;
     public float ShakeDuration;
 
 void tween(){
         iTween.ShakeRotation(gameObject,new Vector3(ShakeX,ShakeY,ShakeZ), ShakeDuration);                        
     }