Forgot to mention - I wasn't familiar with the 9-eyes tall concept. I have heard the head being 5-eye widths wide at the temples tho. But eyes are usually a bit wider than 1 inch. Varies from face to face. So instead of using precise units of measurement like inches or feet, I tend to go by units that are more specific to the figure - such as 7.5 heads tall, since one person's head can be taller or shorter than another person's head. 

Examples:

5 eye widths wide from temple to temple for the face

Mouth corners (usually) pupil to pupil

1 head length from shoulder to elbow

1 head length from elbow to wrist

Face length: length of hand from wrist to tip of middle finger = length of face from chin to top of forehead crest (not the crown as that is the highest point of the skull)

Ears length = distance from bottom of nose/septum to eyebrows, and half to 3/4 wide

Hips = 1.25 head length wide on men, 1.5+ on women

Feet = 1 hand length (wrist to middle tip) from heal to balls of toes (not including toes)

The list goes on. These are proportions I learned years ago in figure drawing basics. Think I was still in high school if not younger. Course that doesn't mean they are as accurate as other measurements or methods. Thing is you can try them on yourself and they are usually correct, so that's why I stick to them the most.

 

~Shane