Anet A8 40 mm fan adapter with 18 mm sensor mount

I've combined two great designs to fit my needs, thanks for both original authors.
Remixed the upper hole to have space for a recessed screw. This way a 40x20mm fan (for example a Noctua A4x20) fits fine with a standard screw.
For sensor spacing and every other info, please see the things shown as "remixed from".

Warning: the hole for the fan duct might need some tweaking to have a perfect fit if you'd like to use your old fan duct. The dimensions should be very close for a common setup, bu