Today, theoretically the day that we in the southern hemisphere should be getting the most PV out of our systems, obviously if no clouds or raining.   

Theoretically yes, but that depends on the panel tilt angle. In the Joburg area that would be around 5 deg for Dec.
Nifty site to get the exact tilt angles.  https://solarsena.com/solar-panel-tilt-angle-calculator/
My panels are at 30 deg and in fact I found that April and September give me the highest wattage. Yes, the amount of available hours are less, but the daily production is about the same as Dec and Jan.