Almost sure that you cannot wire 6 of any panels in series without violating the max voltage of one MPPT controller. So if you wire 6 in parallel you will have a significant shade problem along with 60 amp wires required. With two sets of three in series and two MPPT controllers you'd get the best performance from the 6 panel system and much less amps down to the MPPT. Best to get 3 larger watt panels that will fit your MPPT's voltage spec.
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