Wow what a great conversation is going on here - glad that you've all begun to understand how proportion is so important - in fact as important as body shape in working out what will work for your unique body.
To clear up questions:
It's full head length, not just face length - but a 2D length not 3D - you may find taking a photo - take it with the camera at half your height so that it doesn't skew up or down the apparent length of your body.
A large bust will visually shorten your waist - I - in measurement (if I measured in quarters rather than eighths - would have a balanced waist - but because a large bust sits lower - my chin to mid-bust is longer and mid-bust to waist is shorter - has to be to fit the amount of flesh in!
Waist is the narrowest point between end of rib cage and top of pelvis - so not the belly button (which is lower than natural waist).
Necklaces - that's the Balance Point concept - and is based on face length, not head length (so hairline to chin).
I would love to do a series of posts on proportions so if you'd like to send me photos taken as described I can give you some pointers - will happily blank out faces!