The third version works!
In the second, I changed the nozzle to have about the same opening as the fan to avoid back pressure. But it was too long and the screw holes fickle.
So the third version is shorter and the screw holes got a ring to have some more volume to slice.
The blocked fan was due to my bad bed levelling: the first layer was squeezed wider than the rest. Something a hearty scrape with a knife was able to fix.
