Is it smoking on the middle grate? Looks like you flipped it. Always keep the top vent open. Opening all 3 lower vents will increase your temp, opening and propping the door, will raise the temps even more. If the butt was on top, it would have developed more of a char/barky surface. Have not smoked a butt on the middle grate yet.
Do you have a remote thermometer for internal temps on the meat?
Performer 22 / Copper OTS 22 / WSM 18 / Black OTS 18