I think this duct design is at it's core one of the better options you can find for this printer. It does have overhangs though that would be prone to sagging. I made a version with basically identical dimensions, but with chamfers that are easier to print.
The author remixed this model.
Imported into Meshmixer. Reduced poly count to 20k.
Some light artefacts, but nothing that carries over after slicing.
Made my own design with identical dimensions but more printable overhangs.