1. You would like your sautillé stroke to work more easily.
Sautillé only works if the up-bow is a rebound action, not a separate action.
However, for triplet sautillé (as in the 3rd movement of the Samuel Barber Violin Concerto) the whole arm gives an added impulse on the upbow when the articulation/accent is needed. This is often felt as if the elbow is giving an accent.
2. You would like your sautillé passages to have a clearer sound.
Avoid making a circle shape because it takes the bowhair away from the string. The oval shape keeps the bow more 'in the string'.