I think that it could actually be worse, on a percentage loss. Because voltage is pulled lower by the MPPT. Which would increase the voltage drop.
Assuming that there's enough current available.
I don't think Vmp decreases much in low light. Not nearly as much as current does.
As for my earlier comment that MPPT operating at higher voltage/lower current should help make up for I^2R wire loss,
Looks like 10% reduction in current might be possible, but power is also reduced quite a bit.
What the curves do show is that about 10% change in voltage is not terribly significant; that is why 10s2p with one panel shaded is OK.
Overpaneling is a common way to overcome winter sun angel. But having too small of a conductor, works against that option.
Overpaneling to cram needed production into fewer hours, it works against.
Overpaneling to make up for reduced light intensity (longer path through atmosphere, light clouds, not a problem.
But likely, winter days are often clearer than summer days.
High voltage is the key, but you pay for it (in a DC coupled system). A 250V or 600V to 48V SCC is expensive. A 600V or 1000V to 240Vrms GT inverter is cost-effective.
Of course with AC coupled, you have the option of transformer step-up and step-down. But that is expensive, and difficult to haul up the hill. Better to do that with a switcher. And AC voltages that are convenient to work with are no higher than high voltage PV strings.
