I've always left the skin on until last, I never thought the meat would hold up to cutting under the ribs to remove them if the skin was already off. I wish I could get good at getting the fillets off without cutting through the ribs, but so far can only do it on big, thick fish like bass, striper, and catfish, and then I stop where the ribs hit the skin and leave all the belly meat attached to keep in the guts.