Had a similar question. Just did a 16# packer brisket this weekend on my Primo XL Ceramic.
Low and slow---220-245 for the whole cook.
Still trying to get a sense of the timing. I left plenty of time (had problems with cutting it too close in past) and i've seen a number of different "rules of thumb," the two leading inputs were
1) 1.5-2 hrs per pound
2) 1-1.25 hrs per pound
After trimming, my brisket was closer to 13#; I decided to split the difference and left myself 20-21 hrs (1.5 hrs/lb * 13 lbs = 20 hrs) before the guests arrived. NO wrap during cooking. Paper wrap for resting. Injected with about 8 oz.
As it turns out, I pulled the brisket off at 11 hrs at 198 in the point, 201 in the flat. Wrapped in paper and rested in a cooler with a blanket for 8 hours before serving.
When i did serve it, it was fabulous, though i think a little over-rested. But still warm, great bark, and delicious, and for a displaced Texan in Maryland, it was the best taste of Texas I've had in a while. Very happy with the results.
But this leaves me with one important take away, and one big question:
1) Resting is critical to the process, and as it turns out an extended rest period is not the worst thing in the world; prior to this cook I would have been very uncomfortable resting it for 8 hours. So from here out I'm planning to pull it off earlier, rather than later. This takes a lot of anxiety out of the process.
2) 11 hrs for a 13# brisket is closer to 3/4 (.
hr/lb--Nearly half of what the first rule of thumb would calculate and still in the ballpark of 6 hrs earlier than the second. So why so quick? I was absolutely on top of the temperature, and maintained a stable 216ish for the majority of the cook with one short excursion to 245 max, but brought it back to 225 within about half an hour. Never went back up again. I did not wrap in the cooker at all--only after pulling it off the smoker
So I guess my question is whether others are seeing quicker cook times on ceramics? What rule of thumb do you use?