Just curious... I usually determine the proper 'unit' for a 'word space' in my fonts visually, depending on the font design characteristics. But, I was wondering if anyone uses some sort of formula to determine this instead. I've heard some say that they use the narrowest letter, usually the "i" to determine the "space" unit value. Others may use the "period" unit value for the "space". Half the "figure" width. That sort of thing. And, I would be curious to hear if anyone decreases the "space" width value as the weight of the font(s) progresses.