A few years back, I cooked 9 racks of baby backs in my #2 for a funeral. I used the rib rack in the top position. I believe it could actually hold 11 if stuffed to the gills. Really important to rotate shelves. Otherwise, the bottom protein will be much dryer than the top. Many positive comments from guests, so the final outcome was as expected.
I also stuff packer briskets in without cutting in half. Largest so far was 18lbs, if I remember correctly.
The two can hold much more than most give it credit for. The main consideration when stuffing it to the gills is to ensure the internal temperature probe is clear & no meat is touching it by an inch or so & rotating shelves.
I have never regretted getting the #2 & I have never required a larger unit for any cook that I have had. My #2 was a gift. Saying that, if mine died somehow, I would probably replace it with a 3 just because the cost for the extra real estate is so little.