Update: V3.1 is final. I will not edit again since I am very happy with the result.
Update: V3 adds even more sturdiness.
Update: V2 adds more clearance and its sturdier. Please print screw holes 100% infill.
After many tries and parts that broke I decided to remix https://www.thingiverse.com/thing:2765158 to have a simple to print and yet effective thing to hold a 5015 fan to our i3 Mega
The more infill the better.
Note: for the record I upgraded to Marlin 1.1.8 allowing the part fan power to be 12V instead of the factory 9V. This means that I am using the full power of my 5015 fan.
(Don't you just love the random file names Tinkercad generates? :) )