This is a remix of https://www.thingiverse.com/thing:2274499
I modified the part cooling ducts to fit two 5020 blowers. The exact part number of the fans that I use is Sunon MF50201V1-1B00U-A99.

The heatsink cooling that is linked in the original thing requires too much static pressure from the 40mm fan so I wasn't happy with the results. Therefore I designed an improved version. The duct raises the fan a bit and it is bolted directly in the heatsink holes. It comes in 4 variants:

• duct_heatsink.STL -> simple heatsink duct for 40mm fans
• duct_heatsink_brace.STL -> can be used to also brace the 5020 blowers (makes the whole assembly more robust)
• duct_heatsink_compressor.STL -> integrates a static pressure booster. With this booster I got roughly extra 2-3 m/s of air speed at the heatsink end of the duct with a Sunon MF40202VX-1000U-A99 fan (measured with an anemometer)
• duct_heatsink_compressor_brace.STL -> integrates the static pressure booster and the blower mounting brace

For the heatsink cooling duct you will need 4x M3 metal threaded inserts.
The blowers can be screwed to the brace using some longer self-tapping screws.
For the heatsink cooling duct with static pressure you need a fan that spins in CCW direction. For CW fans print the heatsink duct mirrored.

Note on Sunon fans: The standard PWM frequency of the Marlin firmware is close to 1kHz. This frequency is too low to drive Sunon fans. They have undervoltage detection which is triggered during the "off" time of the PWM signal. For Sunon fans or similar, a PWM with >20kHz is necessary (I use 31.25kHz and can run the fans from min. 20% speed).