I typically don't use a ton of sugar in smoking but find a recipe that calls for brown sugar on top of the fat cap. Hopefully the skin is already removed. If not that'll take some patience. Score the cap into diamond shapes and use brown sugar, salt, pepper, a nice amount of chipotle(if you like sweet vs heat) and some mustard to hold it on the meat. When I'm using hot pepper I mix my season together first and taste rather than adding straight to the meat to avoid over seasoning. Coat the entire piece of meat but heavy on the cap. IIRC I was in the 225 range for a few hours, internal should be 160ish. I think you'd be fine going up to 170 if you think it needs more time. Use fruit wood.
It tasted really good that day, the little chrispy diamonds on top are like little sweet delicious bit of heaven. However, it didn't hold well. Reheating for leftovers was not enjoyable. Be really good with some type of cole slaw to offset that real sweet and savory flavor.