Jan 21: the top part is done. I am following directions for the smallest size, which actually fits my 10-yr old with some positive ease for growing. I used up three full skeins of dark gray, and probably a quarter of the other two.

Done!
I followed directions for the smallest size, but ordered less gray and black yarn - and was right!
I used up pretty much all 2 skeins of black, but only 350g of dark gray. Additional colors use less then half a skein each.