Yes the connectors are not super easy to solder, you need magnification and a steady hand but a 30$ stereo-microscope totally does the job here. If you did SMD before and feel ok about it you will have no issue.
Below is a trick to get the alignment right when hand soldering.
The project is now uploaded to https://hackaday.io/project/175832-minimal-raspberry-pi-cm-4-carrier
and the PCB files to https://github.com/PTS93/Minimal-RPi-CM-4-Carrier
Please keep in mind this is nothing but a quick and dirty demonstration. Especially the routing is far from good and completely optimized for CNC milling, nothing you wanna copy
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