I made a pork shoulder by marinating for a few hours in Char Siu sauce (chinese rib sauce), then popping into a 250 degree oven overnight. Gently reheated for dinner tonight. The meat was great -- fall apart tender, not dried out, about what I expected. I was also expecting, however, that the skin would get crispy -- turn into cracklings/chicharrones. It was certainly well cooked (most of the fat had rendered out), but was inedibly tough -- like leather. Did the slow roasting preclude edible skin? Or did I do something else wrong (maybe the dry heat)?