I'm not sure if I'm asking for the recipe to the secret sauce here, but how does air flow through the Englander NC-30? Obviously a good portion comes through the hole at the top of the doghouse/zipper thing, and the secondary tubes, (edit: and the air wash) but does it come from anywhere else (assuming good seals and capped ash chutes/doors)? What about the curved plate around the dog house? And when open/close the air intake lever, does it affect all of them equally?