If you hang a chicken, leg end down (there is a reason this is better) then the column of hot air rides along the length of the chicken. If you have it flat on the grate, then the column of hot air hits the bottom of the chicken and has to wrap around the chicken. If you think about airflow, it will be smoother if it is hitting the rounded end of a chicken half, then the flat bone side cavity of the chicken half. Now, if you think about how a chicken cooks in a wood fired oven, any meat for that matter, you can see that the PBC, or any vertical cooker with the meat hanging, approximates a traditional wood fired oven, with a chicken on a rack (for me, the ultimate roasted chicken cooker is a wood fired oven, there is simply no better chicken than that). Wherein the hot air flows over the chicken surface. You simply get better rendering and better skin texture.
There is no such thing as self-basting meat, and that is fine. I think the need to baste meat may well be a myth, other than for appearances sake.
I saw in that video how they did a 13 pound packer, they do use two hooks. It makes sense.
Whip It Off, Chambers!
"perhaps...but then again...maybe not..."