I purchased some Odroid-HC2 SBC's to use as a NAS, only to discover that they run fairly hot.
I designed this fan mount to add a 120mm fan for cooling a stack
...Plus of 4 HC2's while remaining fairly silent. It slides over the aluminium cover, and the "legs" prevent it from falling off.
Print with the flat side against the bed, and "legs" facing up.
Holes and hexnut cutouts are designed for M3.