I have had my MES for 10 months and smoked several shoulders. Before the MES I used a horizontal charcoal smoker and wood chunks. I got more smoke penetration using charcoal and chunks. I traded that for the ease of operation with the MES. As you know, psychobrew, you can only use chips in the MES. For whatever reason, in the MES, smoke seems to stay on the surface of the meat rather than penetrate. None of my briskets have ever had the smoke ring I got on the horizontal smoker. But I love my MES. All I have to do is add a handful of chips every hour. No futzing with a gas flame or babysitting a fire! So the answer to me is to make more surface area by cutting the shoulder into smaller pieces. Therefore, more smoke covering the meat. I try to get four equal pieces.
As to cooking temps, the critical point is 160 degrees to 190 degrees meat temp. This is when the tough tissue breaks down. You want that to be low and slow, about 225. Getting up to 160, well, I push it there at max heat for the MES, 275 degrees, until the 160 mark, then 225 degrees until done, about 190. I have pulled the shoulder off at 185 with no ill effect. Keep the top vent fully open for good airflow. Fifteen hours is about right in my experience. And don't forget to wrap in foil, then old towels, and park the meat in a cooler for at least an hour up to four hours, before pulling. Makes it even more tender.
I bet your family/friends are lovin' all that great smoked food! My new discovery is hot smoked salmon, a whole side at a time. Tasty and heart healthy!