Ok something odd - rereading your post I went back to the online calculator.
If I put in my 4S3P string using the Jinko 580W panels and TURN OFF the oversizing toggle it allows a 250/100 mppt.
If I put in my 4S3P string using the Jinko 580W panels and TURN ON the oversizing toggle it says to use the 250/85 mppt.
Why is that ? What is going on there ??
Something else very odd - at least to me - if I put in 4S4P this is allowed using the 250/85 but NOT the 250/100.
What is different about the 250/85 vis-a-vis the 250/100 Mppt ?
I would have thought that the larger 250/100 was better suited to over paneling - yet the calculator does not allow it. However If I toggle on allow 130% over paneling the recommended Mppt is the lower rated 250/85 …
PLUS
…the 250/85 WILL ALLOW 4S4P which is the 180% over panel we have discussed here.
I am now officially confused.