The pictures help.
Good choice on the paint to show the heat areas.
So only two air entry nozzles on this just as you text described, eh?
A Doug Williams learners system uses three nozzles. Add in another three between those, reducing inlet end holes really zooms-up the performances.
I hate anymore to see more than 4" (100mm) between the in-hearth nozzle ends. And no more than a 3/4"-1" (16-25mm) nozzle end protrusion past the wall; or built up ash slope. Wider spacing; longer protrusion lets upper pyrolosis gases (smoke&tars) to sneak past the fiery intense oxidization front of nozzle tips plane. Weak gas then with lots of noncombustible steam/water vapor and unconverted, noncombustible carbon dioxide.
Suggest you immediately add in at least two more nozzle pipes between the existing ones. Added ones only would have to be 1/2 or 3/4 pipe with male threaded inside protruding ends. Pipe cap these with black pipe, or SS caps drilled out to the actual figured air-let in. Ha! Now you are a Mukunda nozzle system.
Best to inside cap plug the other two existing with the same drilled holed ends.
Then Wayne Kieth style top light down from the top through a poked down into the char bed hollow digger-pipe.
Next performance-up improvement step then is to re-capture for the air-in heating all of that shown center and lower systems being wasted heats.
And that is where a lot of effort can be wasted to make an air tight common nozzle recovery area on this limited life system.
HAS to be air tight so you can shut off the inlet air for system shutting down and not have all of your critical char-bed burnt up by the next usage.
Heats recovery and utilization. Ash sloped metals shielding. Easy pull-out, drop-in replaceable sacrificial internals are all features that separates out the will-work; from the will-work-and-live-usable-life, with minimal repairs systems.
tree-farmer Steve unruh