"Place the violin to suit the length of arm. Too far to the left and the player won't reach the tip of the bow easily. Too far to the centre and the bow will be quite crooked."
Players with shorter arms need to have the violin more towards the centre. Players with longer arms can move the violin more to the left.
The teacher can help the student find the best position of the violin by placing violin and bow for the student, as shown here.
Look for a violin placement where you can reach the tip of the bow without pushing the right arm too far forward.
If the arm is pushed too far forward to reach the tip, this creates problems not only for balance in the body, but also for bowing in the lower half of the bow....