The cooling of the coldend was unfortunately a bit too weak in my tests.
I am very satisfied with this duct so far: https://www.thingiverse.com/thing:2751027
A fan duct for using 40mm axial fans.
I have very much airflow under the nozzle - already at 50% fan speed.
When the nozzle is heatet to 190°C and the fan starts at 100%, the temperature drops just 2°C. Could be readjusted by PID, but that's ok for me.
Support from printbed.
You need to rotate the part horizontal by 45 degrees to get a good direction of the support to hold the diagonal part-fan mount AND the "channel" for the extruder cables and the bowden tube.