Be carefull. a coal fire follows the air. If you intentionally leave an air gap under the hopper lid on your stove, you will be allowing fresh air to enter the hopper, and the fire will travel up into the hopper.. causing lots of potential problems,, like warping the hopper, overheating the stove etc etc..
We have a forum member with a Hitzer 503, in western Michigan, near the lake, he has constant high draft.. His hopper lid gasket was loose and he had some fines holding the lid up a little bit.. he had the fire burn several inches up into the hopper,
So be carefull with your experiment..
As long as the mini-puffbacks and small,, just think of it as your stove muttering or snoring..