The science of anatomy and proportions is an incredibly difficult subject and I seriously doubt that anyone is going to understand it properly without a lot of study. The reason being that there is no such thing as the "average" figure, and any variation in size of figure is far more likely to be FUBAR than devious intent
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There are so many factors that go to make-up the build of a figure. Taking a hypothetical adult male, is he a testosterone filled 35 year old who habitually stands to attention like a guardsman, or is he 57 with the weight of the world on his shoulders? Is it 9.30 in the morning or 10.00 at night? Things sag! There are no definites and that is why the use of "heads" as a GUIDE to proportions works so well and has done for such a long time.
Going back to the hypothetical male, if you want to sculpt a hypothetical 1/20 (90mm) figure, for the sake of argument, take as a starting point 8 heads. Set your calipers to 1/8 th of 90mm, then build your armature and design your figure accordingly. If you want young adult, perhaps make your figure 7 heads, if you want large athletic and imposing, you might go to 8 1/2 heads. If you want squat, or old or elegant or fat, adjust the number of heads in your figure accordingly, but keep your calipers set at that original 1/8th of 90mm.
The best advice I can give is buy a good Artistic Anatomy book. Computer screens are fine, but there's nothing like the feel of a real book.
Here endeth the lesson,
. My brain now hurts, soooo............
Best wishes, Gary
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