Water meter interface mount

Summary
For my home automation system based on a Raspberry Pi running Domoticz I decided to build my own water-meter interface. I reused a sensor from an older thermostat (a Toon 1) that was used to monitor the output of a solar inverter. It comprises a (blue) led and a light sensitive transistor in a single package, sporting a 3.5 mm receptacle for connection to the Pi. A small interface (not described here further) was designed to drive the led and present the output of the sensor to a digital input on the Pi after suitable conditioning (Schmitt trigger with hysteresis).
The sensor is mounted in a modified lid that basically offers a bit more space to accommodate the sensor. The lid furthermore adds a mounting for the sensor (is a tight fit and no other means are needed to fix the sensor). This design is the first prototype I made, and it worked like a charm, so I didn’t bother to refine it. The design shields the sensor from other light sources (although I have not experienced pr