The single fan duct on the Adventurer 3 is pretty rubbish.

I've designed a dual fan duct that splits the flow so that both sides of a print are cooled. The results speak for themselves. The original duct is on the left in the overhang tests. Ignore the top few layers. The modelled curled up so much the nozzle ran into it and knocked it over.

There are two versions of this duct. The normal version, which provides excellent cooling, but may impact the raised edges of the bed (which does raise the question of whether the normal duct does as well), and a "raised version", which has been lifted around 2mm and will hopefully not hit the edges of the bed if you run too close.

I'd print this duct out of ABS as it sits pretty close to the nozzle, with supports from the bed only. It is already in the correct orientation for printing.

If your printer accuracy is decent, this should just be a direct drop in replacement for the original.

This was sliced with Cura. I've included full profiles (as ,3mf projects) for both PLA and ABS.