I'm a big fan of the GeeekPi Rack Mount Kit for Adapting RPi 4B's to a typical Rack but I needed something a bit more flexible for a few RPi 5B's I was integrating into it.
I wanted compatibility with this under-mounted Geekwork NVME adapter but it wouldn't work with the included adapter plates so I made a modified part.
The author remixed this model.
Used the RPi 5B Model to help adjust the tolerances on the openings, most of the model is purely original with most of the original versions calipered off real parts.