What I dont understand with this experiment is that, shouldn't there be no space for air to enter there at all ? I've noticed the stem doesn't seem snug at bowl end when closely inserted . Or does it fit snug and its just that I can't see down there when it's on . I assume not seeing holes on the side of your stem . Wouldnt that gap between roasting tube and LB joint be a heat loss of some sort ? Wouldn't resizing the hole or roasting tube seal things so that all the heat can go directly to the load ? @Alan probably has some insight on this ? I am confused, lol. I suppose the "gap" can perhaps serve as a air hover space for it to group and shoot up the tube?