Installation of my board was without issues (other than the filtering issue, which was corrected before installation.)
The box everything goes into is an Elk Products box with integrated battery charger originally designed for the alarm industry. It's basically a pass-through, and uses the battery as a cheap regulator. Nominal output voltage is 13.6-13.9, which is what the battery is floating at during charge, so everything in the box needs to handle this.
Starting at the top right, my board, the built-in battery charger, the battery, the power transformer (12.6VAC 2A), terminal strip and fuse, and the final component which is a commercially available water leak detector, "The WaterBug," available from Winland Electronics. The wireless sensors being powered are off to the right (out of frame.)
Everything powered up with no issues, and has been working reliably for the last few months.
The box was installed in the furnace closet, with the leak detector going down to the water heater directly underneath. (Lid removed during installation.) The only addition was to hang a temperature/humidity sensor in the box and connect it to one of the wireless sensor units.
(Apologies for the picture, it was taken in the dark with a potato!)