The old Replicator 2 Duct works well. However, outlet velocities are noticably high and there's a strong forward current. That, and the fit was never great, just okay.

2 years, and time for an upgrade through Computational Fluid Dynamics (CFD).

Bigger plenum with 13 jets in a box C configuration. Hot end nozzle correctly centered in a uniform turbulent air mass. Larger downward flow area for improved filament cooling.

Better fit, tighter and way more level. Tweaked and checked, until it was sweet and east too print.

Faster STL. Minimized curves to reduce file size and speed CFD calculations. WIN WIN.

Less expensive. Technically still free to download, only even more added value.

Enjoy :)