I really like the original model, made some adjustments to make it even better:
Added a spring mechanism that will clamp more tightly on the DIN rail. Should allow for DIN rail made of sheet metal 0.4 - 2.0mm
Easier access to swap SD card
A notch which prevents the retaining tab to snap of if too much force is used. This doubles up convenient spot to push to remove it from the rail again.
Made some more room where the USB plug sits
There are two versions, one to use with 2.5mm screws, and one for 3mm screws. Use 2.5mm if you can. I only had 3mm screws around, so I drilled the Pi PCB to make them go through.