With a big Thank You to you all for the various inspirations how & where to mount the uRADMonitor, I opted to install my Model A a bit sheltered.
Not as much to the rain and/or snow but rather temperature.
As I would be installing the uRADMonitor on a wall facing east-ish.
I considered closed (IP65 or better) boxes but expected that could (perhaps only a wee bit) impede the detection-rates.
The uRADMonitor is designed for open-air installation for a good purpose
I also looked into an empty Rittal Ventilator box (11.8cm inside-measurements) but that would create a bit of a challenge as the connectors to the uRADMonitor would be very close to the edge of the box (read: probably needed to cut-out a hole) contradicting (a bit) the purpose to shield the uRADMonitor’s connections. (although one can come-up with some additional shielding in that area by glueing plastic slats in that area, for example)
So ultimately I opted for the Davis Instruments Passive Shield #7714 as that is relatively affordable & available.
Where I needed to cut-out the center-section for 2x more (of the included) plates so I could diagonally/slanted install the uRADMonitor.
For the ethernet connection I used a CAT6 flat cable for the moment but will replace it to thin white cable (CAT5e, CAT6 or CAT6A) once I have my data-rack into its final place (read: get more accurate length-measurement how much cable-length I actually will need)
Of course I also used the passive POE Injector as already depicted on this forum, that works great in simplifying the installation. (read: cabling)
IF so requested I can put-up more detailed pictures & descriptions how I did things.
I leave that up to the community.