60mm fan duct for UP Plus2 and Afinia

I have tried installing several fans in order to reduce the temperature of the step motor of my UP Plus2 printer.
I tried a 40mm fan duct I found here in thingiverse but the design was really bad (don't worry, I will not show up the name). The model itself was well designed for printing, but the author didn't take much care about the physics of fluids. I used a good 40 mm fan and found out that the flow around the step motor was really low, do to the internal design of the model: the flow is no