My wife claims that most people are as tall as the distance from finger tip to finger tip when they stand with their arms stretched straight out. If that is true you could place a figure in a square template to check proportion for arm length. I have noticed that for the most part head and trunk size is the same person to person and people are taller or shorter based on the length of their thighs and shins. I have not figured out how arm length fits into it but it does seem to me that most people's arm length is such that when they put their arms down straight their wrist or palm is in line with their groin...