Awesome stuff. I meant to say thickness earlier rather than weight.
So its pretty funny, and strange. So the default size of the race of the civilization determines the weight of the armor and who can use it, but the actual size of the wearer determines the thicknes of the armor. Confusing.
Also, there's some sort of grey area within which you can wear armor of improper size. I had a Masterwork Dwarf (70000 size) wearing Masterwork Human (75000 size) plate, and he became a FTN lich (65000 size) which could still equip human plate, whereas elves (60000 size) cannot wear vanilla human/masterwork dwarf (70000 size) armor. The size difference is in both cases 10000.
Interesting that these findings mean the size 65000 lich will have his plate become ultrathin, vs a "large for an olog" olog wearing the same armor, gets HUGE protection.
Also, I wonder where 'deities' get their clothing from, since they definitely cannot wear the items their civilization produces. Only a demon, titan, or forgotten beast can craft items that are sized appropriately, and Hell-demons are naked, and deities lack any weaving skill, so there has to be an escaped demon somewhere, madly knitting. In one memorable worldgen, a male and female version of a "unique" demon race escaped Hell and happened to settle in the same town, married, and had a total of seven children.
I kinda think a really cool mod would be to make sure all items have equal thickness (despite the heaviness; this will probably mean legendary armor user or bust, but oh well), and have exactly enough space for one over armor and one under armor slot, the first to attempt deflection and to turn edged attacks into blunt attacks, the second to soak up blunt impact. And of course, maybe something to make arrows observe armor.