What is the proper procedure for adjusting the headrest (apoyacabezas) to prevent whiplash (efecto latigazo) in rear-end collisions?

1. Position it as low as possible against the neck base
2. Position the top of the headrest level with the top of the head (or eye level), with a maximum distance of 4 cm behind the head
3. Remove the headrest completely for better rear visibility
4. Tilt it back at a 45-degree angle