Doug,
Below is a whole bunch of my Prime Ribs I've done over the years.
You will notice they are all about 5 lbs, give or take a pound, because that size works out best for us.
You may also notice that they all take about the same time to finish, to Temp.
I've tried between 135° and 144° Internal Temp finish temps, and we prefer about 142°-143°.
I use 220° smoking Temp now because it's low enough to make sure the whole thing can end up the same Pink color from Bark to Bark, without having it Pink in the middle & Medium Gray around the outside up to 1" in. This Gray around the outer portion is from using too high a Smoking Temp. Apparently some people like this, until they follow my method. Then they are hooked forever.
NOTE: Your 11 pound will only take about 1/2 hr to 1 hour longer than my 5 pounders, because with a Prime Rib it's the Thickness that matters. A 5 pounder can be the same thickness as an 11 pounder. The only difference is the length, and the length doesn't mean anything. The only reason it will take a little longer is because of the bigger mass of meat carrying a lot of "Cold" for the first hour or so in your smoker.
So use any of the below examples. They are all similar, but the newer ones may be easier to follow, because I got better at writing them up over the years.
Enjoy,
Bear
Prime Rib Calendar (14 Smoked Prime Ribs)
Smoked Prime Rib (Double Birthday Dinner 2017)
Smoked Prime Rib (47th Anniversary Dinner)
Smoked Prime Rib (49th Anniversary Dinner)
Smoked Prime Rib (First of 2017)
Smoked Prime Rib (Apple Smoke)
Smoked Prime Rib (New Best Ever)
Smoked Prime Rib (Another One)
Smoked Prime Rib (Great Stuff)
Smoked Prime Rib
Smoked PRIME RIB (Multiple Woods)
Smoked Prime Rib (Panned)
Smoked Prime Rib (Panned #3)
Smoked Prime Rib (Easter 2018)