I saw some stoves like this on U-tube and I thought that pre-heating incoming air actually means "cooling" the fire in the inner container. OK it may seem like the same loss if you have only one wall, but remember there is a draft of air rushing to go in, thus cooling the flame chamber a bit more.

Instead, I have been thinking more about adding more insulation to the stove wall and using the rocket stove principle.

So, far I have stopped at one wall rocket stove, and instead of spending time on improving it, I am actually USING the stove for other projects like burning paint and rubber coating off other metallic stuff that I want to utilize in other projects.