Probably had nothing to do with the UDS. Sounds like it performed flawlessly. My thoughts are you pulled the butt too soon. The magic for me is to pull between 200 and 205 degrees , wrap in foil and let it sit in a cooler for at least an hour.
55 gallon smokin' UDS
BBQ Grillware vertical gas smoker
WSM with mods
ECB Deluxe (scrapped for parts for the UDS)
BBQ Grillware gas grill
Pro-Q Exel 20
High Desert BBQ