The philacry are humans with wings like dragonflies, crystal clear and barely weighing anything, yet able to withstand the rapid wingbeats of flight. Though they can fly from childhood, buzzing about with some of the dexterity of dragonflies, this takes a lot of energy, and a lot of oxygen, leading to the same respiratory system that birds have.
The question I have, is where could you store air sacs in a mostly human body? Birds have nine air-sacs, but maybe philacry could manage with less? I guess it's possible to have less of them and make them larger.
I didn't want to shrink too many organs, so I wondered if I should lengthen the torso. Or, maybe you could put them in the buttocks, and make them literal balloon butts? I was considering putting them in the chest, so that the philacry were mistaken as an all female race like harpies, when really it would just be moobs. That's my thought process ATM.
Question: Where could I put air sacs in a human body?
Further details would be how many we could put in, and how large they would be.
Thank you so much!