I have designed and printed it and pretty sure it will work for 120mm slim fan. Unfortunately 15mm thickness still not slim enough to put back the cover, I will add photos later if I can find slimmer fans cheaply, most likely 12mm thick fans should work. In the meantime, I am using this 2x 5010 fan design https://www.thingiverse.com/thing:5196689
Mounting holes are slotted to enable easy assembly to avoid fan blades and adjust to your preferred position.
If it works, I would appreciate sharing your makes.
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The author marked this model as their own original creation. Imported from Thingiverse.