You need to keep Voc of the strings below the PV Input Vmax of the MPPT.
This is because the way the inverter reduces the power being supplied by the panels is by increasing the voltage the MPPT operates at. Effectively the MPPT reduces power production by increasing the operating voltage in order to choke the current.
If the panels can push a voltage above the Vmax of the MPPT, things can (and one day probably will) go pop!
Next thing you need to take into account on this front is the edge-of-cloud effect. This can boost the Voc of the panels by 10%.
So unless you are trying to squeeze every last watt, set up your strings so that their Voc do not exceed 90% of the Vmax of the MPPT you are connecting the string to.
The rest of the equation relates to derating factors - angle, temperature, solar radiance per square meter. But if you leave some margin on the Voc and make sure Isc is less than Imax of the MPPT, relying on the standard label values of the panel should keep you out of trouble. If you are getting close to the limits, best you take a closer look at V-I curves and derating factors in the panel datasheets.
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