The kiln design approach seems to be an efficient Bourry Box grate coupled with a tall chimney.
Kiln dimensions (from book?)
Kiln building in Germany
German firing results
Sarah Villeneau/Manor Oaks Sheffield - Kusakabe kiln
Rudy Meyer - Kusakabe kiln
Cher Shackleton - Kusakabe kiln
Wood and charcoal designs
High efficiency French design
At La Borne https://www.laborne.org/en/le_four_girel_au_ccclb-2/
Sheehan design built by Loren Scherback
Kiln design seems very similar to Kusakabe. Lots of info in the drawings and sketches.
Building and firing the kiln
But also smoke is inefficient firing, and isn't required for reduction - see also the presentation by Engels at the wood firing conference in La Borne.
Smoke gets in your eyes - John Baymore