Koshini is a sort of halfway toonish character, and her hands are not
really meant to be realistic.

I just now tried scaling the hands, and you're right.  They do scale up and
down, but they also distort badly.  It appears that the joint setup is
wrong.  I also tried a crossed-arms position, and found the same problem. 
The shoulders go weird, and there doesn't seem to be any combination
of Front-back and Bend that will reach the crossed-arms position without
this distortion.

I'm afraid the only thing I can recommend is to use another figure!

You could try the figure I use for my avatar... she's all the way toonish,
but her joints behave properly and she's free. 

Edit: There is a Koshini 2 figure; I don't know which one you're using,
but it's possible that the version 2 has solved these basic problems.
Somebody else will know the answer to this!

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