I have also found recently that Costco loin backs, from Swift, have a large piece of the lean loin left on at the large end of the rack, which turns out dry no matter what I do. Very disappointing, and I'll be going back to Sam's for my loin backs. I do my ribs at 225 for about 5.5 - 6 hours depending on size, no wrapping but I do flip them over (meat side up to meat side down) about halfway through (don't ask me why, it just makes the top look better when I bring them in). Usually the meat is bite-off, not fall-off, just the way I like it. Except for those Costco racks, no problem with dryness.