I have modified ktapper's Duet 2 Maestro Enclosure that was very well made, BTW, to add many extra vents. I crudely added the vents, but, they were very much needed. I had trouble with both Fusion 360 and DesignSpark Mechanical in adding holes to this .stl file, so, I had to go with the convoluted Tinkercad. Therefore, to simplify things the vents are rectangular prism holes, because in short, Tinkercad sucks. These Duet Wifi/Duet Maestro/Duet Ethernet boards build a lot of heat on the bottom, which is in the design specs of the board. Ktapper had a good design with the horizontally positioned 40mm fan mounts and the mild ducting, but, it wasn't enough vents for my liking.
My remix is just the same design, but, with way more vents. I added vents to the bottom, for maximum heat dissipation, as well as to two of the sides. I was still trying to maintain some of the flow properties designed with the fan positioning and ducts. I have not printed this yet but, I plan to soon. My first attempt at adding vents to the bottom, I made them way too long spanning length of the case. This would have weakened the structure, so, I have since separated the long vents into 3 rows of vents on the bottom, which, shouldn't detract from the rigidity of the enclosure.
Next I will be adding a cover, since, one was never created for this case. I will likely build a fan into the cover as well for cooling the stepper driver heatsinks on the board.