+1 to Grampy. We hear it's always better to cook meat on the bone. And it's true...for practically everything. But one cut of meat where it doesn't make as much difference, its pork butt. There is so much intramuscular fat and connective tissue, even with the bone removed, it will cook up moist. Similar "cheap" cuts of pork and beef are also less reliant on the bone. I think you figured out the key to boneless butt. Tie it up. With the bone in, it keeps a more compact shape, with less surface area to lose moisture. Once you take out the bone, it creates an irregular shape, and reveals more surface. If you tie it, you reverse that.