2×11 lbs pulled pork picnic shoulder timing question

Hi everyone,

I found some answers to my question in the subreddit but wanted your input as well.

I have 2 bone in pork picnic shoulders 11lbs each and I'll be smoking them for Saturday dinner and I'm debating when to start and put it on the grill.

The game plan is:
Low and slow
Double indirect with deflectors on bottom and pizza stone on middle position of divide and conquer
250-275f
KJ C3 with the grill grate extender (one on top one on the bottom)
Salt dry brine overnight
Foil boat after 165 until the end? (Depending on the bark, dryness)
Rest in FTC between 3-5 hours
Target time for dinner is between 5 and 6pm on Saturday.

Now, since I never made shoulder of this size and now I have two, I really don't know how long this might take. 12 hours? 16?

Im flexible with time and if it's done sooner than planned I can just rest it longer in FTC but I want to avoid it taking too long to the point where we miss dinner.

I'm thinking about starting to smoke at 9pm on Friday and dinner at 5-6pm on Saturday.

Anyone has experice with something similar?

Also, will the grate extender make a difference in terms of temperatures inside the dome?

Thanks!