First, when making my chicken for shredding in the pressure cooker, I looked on the Internet for suggestions how long to keep it in. I saw a top google result blog post on shredded chicken which was going on about how difficult it is to hit that sweet spot of juiciness in a pressure cooker. I used that one against my better judgement, and ended up with chicken which is cooked enough to eat, but not well shreddable, and the dark meat is still tough.