I suspect that the 30A fuse recommendation was made for the power of the panel(s) without consideration or knowledge of the tiny wire size in the circuit. That was unexpected, the assumption here was a 10 ga. minimum wire.
The crucial difference between most NEC (Nat'l Electrical Code) based charts and the charts that should be used is that they are for AC, not DC. AC allows the wire to cool during the vast majority of the time that the circuit is not at or above the "RMS" current. The NEC's values are set such that the length of the circuit is not a factor.
A true DC chart is a grid with current and circuit length deciding the minimum wire gauge. This is the sort of ampacity chart that should be referenced for DC voltage:
http://www.ancorproducts.com/en/resources/three-percent-voltage-drop
If a 10% Voltage drop is acceptable then:
http://www.ancorproducts.com/en/resources/ten-percent-voltage-drop
I would strongly caution against using the 10% chart with a solar system, you want everything that you can get. Can use it for things like light circuits etc.