So how light is Unnaturally Light
I have a elf tiefling so i based the weight of elves because the normal tieflings have the same as humans. So I did some calculations with a base of 10000 elf's mails and females
Variable Mean StDev
M ELF H 187,40 8,30
M ELF W 62,176 4,408
F ELF H 182,24 6,07
F ELF W 50,347 3,300
So I can calculate the lowest 1% of all elf's or should i take a value that is 50% lower then the lowest value or something.
So what do you think Unnaturally Light is?
Imo, unnaturally light doesn't have to mean the raw value of weight is lighter than the chart. I think it can also mean your person is just substantially lighter than they appear.
For example, let's say a 6ft 2in human male weighs (on average) 200 pounds. The unnaturally light tiefling vs of this person could be 130 pounds or something.
If you want to use numbers, I'd use a combination of what you've done and my alternate approach. Perhaps you could design your character to whatever your mental image is, guesstimate the weight they "should" be, then apply a percentage reduction.
As to what exactly that percentage should be, a 30-40 percent reduction is my suggestion. More than that wouldn't be unreasonable though.
Hope this helps! :)