The limit of size for the head is currently:
0.05 H_top <= H_head <= 0.25 H_top (L384-395)
After a quick measurement, the human ratio is rather 0.2. To give a better idea of the number involved, for an adult size robot of 160cm of height, the distance between the first axis of the shoulder and the top of the head should be between 8 and 40 cm while for a human, 30 centimeters seems reasonable.
Given the number of head we cut the past years, I propose to change current rule to:
0.1 H_top <= H_head <= 0.3 H_top