I do want to show off a little 
, but mostly I want to share what worked for me.
I was having HA Yellow on CM4 with an SSD, so I used as migration tutorial the: https://support.nabucasa.com/hc/en-us/articles/25608040264093-Migrating-from-CM4-with-NVMe-to-CM5-with-NVMe
But learning that the temperatures are more aggressive on CM5, I decided to put a 12 V fan for cooling. My HA yellow box sits in a place where I don’t care about the noise, so … what I did:
- Found (on the public schematics & pcb layouts) a 12V pad on the PCB (and a GND)
- soldered a small connector
- imported and adapted the case from Home Assistant Yellow Enclosure by Home Assistant | Download free STL model | Printables.com (which was already adapted a little bit for easier printing) to support a cooler and to have air-holes for air-out
- I 3D printed the top case (with a semi-transparent PETG material to be able to still see the LEDs inside) , added also the heat-set threaded inserts
- I used the rPi radiator “COMPUTE MODULE 5 PASSIVE COOLER RASPBERRY PI”, which came with thermal pads already applied, and I used the screws + plastic spacers included in that box
The rest you can see in the pictures.
The most important for me: It works well ! and … temperatures dropped by ~20 deg 
CM4 -> CM5 with fan
usually: 52°C -> 31°C
esphome compile max temp: 67°C -> 44°C
Here are the photos:
