The project continues, albeit slowly.
Some inexpensive DC-DC boost converters have been very slow from China, though multiply source, they have not yet arrived.
An older module which was on hand has enabled progress of reliability and battery trials.
Above is the current prototype. The module on the white plug in cable is a 4-20mA simulator set to 20mA for maximum drain during battery trials. The module at upper right of the pic is a TP4056 batter charger and 1S protection board for the 2000mAh LiPo. The PV array (partially obscured) is capable of 80mA of charge current in full sunlight. The prototype includes a red LED drawing 1mA, an additional 24mAh load per day.
Starting with a fully charged battery, the system was run for four days without sun, and then charged in full sunlight. It reached full charge is just under four hours, so long term average of one hour of full sun per day is sufficient to run the system. At around 80mAh/day consumption (including the red LED), the 2000mAh battery has an endurance of 25 days.