This is a simple model I made to hold my doorbell camera flush with the gate post. I made provision for a USB charging cable from a solar panel to keep my doorbell camera charged. As I had to modify the backing plate for the doorbell, I did not model any holes as I simply drilled the holes and used self tapping screws to attach the doorbell. The original model I made should work with a 75 mm deep post. I have included the FreeCad file so you can modify as you see fit. Printed with the cover on the build plate, but mounted with the cover on top, to prevent rain ingress.