I hadn't tried banking the charcoal along the outside of the kettle. I just use the charcoal baskets on each end of the grate.
I was thinking about the heat rising too but in more general terms. By that I mean heat rises and cool air falls, as we all know. In this case, it's all hot air rising but the heat that traveled the furthest from the heat source/coals is hotter than the heat right near where the coals/meats are.
And who said BBQ isn't a science and un-sophisticated? Haha. I don't know. Maybe my reasoning is off and I'll have to check a high school science book or something.