I made this model about a year ago but never posted it. I had a case that would allow me to mount my Octoprint instance on the bottom of my Lack Enclosure but it did not allow for a fan or PoE hat. I took inspiration from Raspberry Pi 4 1U rack-mount bracket over on Thingi. 

There are a couple of issues that I might fix if there is enough demand:

• I did not think about the MicroSD card sticking out the back end until I actually printed it out. I added a notch in the back to account for the SD card.
• In adding the notch for the SD card, the sled can now get pushed farther back which partially blocks the USB C port. If you are using a PoE hat to power the pi, this is not a problem. Otherwise, you might not be able to push the sled in all the way.
• One of the MicroHDMI ports is blocked.
• The sled has a small tolerance. You may have to slide it in and out a few times for it to slide easily.

Overall, I am happy with the model for my needs.