I decided to go ahead and get a post started, since Day 28 might wind up bleeding over into Day 29. I got a very late start this morning and didn't get my roast on the grill until nearly noon. I'll come back and update with the final product at whatever time it winds up being done tonight.
About 4.7 lbs of boneless shoulder roast, tied up, and having sat in a rub of chili powder, garlic, salt, and a little brown sugar for a day or so.
On the grill ... cast iron diffuser and aluminum drip pan at the ready:
6 hours later, holding a stall at about 167°. I bumped the temp up to 300° and we'll see if we can get this baby off the grill before midnight.