Thanks.
The fact that the series setup will kick in during lower light levels than parallel is barely mentioned in all the material I have read.
So far, I have been unable to find a curve showing voltage and power output vs light level for any solar panel, so cannot quantify the benefit

One key question is "How many more hours/day generating is gained with 2 in series vs parallel?"

What fraction of total rated panel capacity do you see in a cloudy summer's day?

Location will be important. We get well over an hour of twilight night and morning here, whereas in the Caribbean we will have about 5 minutes.