Putting the panels in series will make very little difference to the charging early in the morning, or late in the day.
By the time the panel voltage has dropped below the battery
voltage the amount of current
the panels can deliver is very small.
Have a look this output. Very late in the day when the panels are only capable of 0.6A the MPP (Vmp) voltage is still 15.0 v ( the maximimium voltage the panels could produce would be higher again)
In the second photo
the controller has actually shut down because the energy from the solar panels
is less than the energy the controler needs to run.
Notice the voltage is still high (Voc) at 18v despite the very low light. These results are typical. It's not low voltage that shuts the output down if there is no shading.
The difference between series and parallel shows up with shading there is almost no difference to the low light performance.