I remixed agiler's design so the air intake is only below the stepperdrivers, following the recommendation in the user manual of the duet.
I also updated the top to remove the extra intake, but didn't test or print it myself. I used the 60mm top by OderWat: https://www.thingiverse.com/thing:2981976 so no air is blown against the bed. It fits perfectly except I had to drill some new holes for the screws.
I used the 60mm fan from the powersupply on 7v with a buckconverter making it nearly silent while still moving more air than the default 40mm fan.