Push it or no?

The NEC requires wiring and fuses to be 1.25x max continuous expected current:

33..72 * 1.25 = 42.15 amps rated wire/fusing/breakers

NEC also requires an additional 1.25x derating for solar--Or 1.25*1.25=1.56x derating (allow additional power for edge of sun, high altitude, etc.).

1.56 is a lot of derating, and would seem to be excessive. Check the manual(s) for your devices and see what they recommend.

And you have to look at the voltage drop too... Adding more current gives you more voltage drop--Which can be an issue itself (and frequently why we have much heavier wire than would normally be found in a standard 120/240 VAC power system).

-Bill

For your system, the Controller to Battery Bank, 60 amp MPPT controller, 60 amps * 1.25 = 75 amps ~ 80 amp branch wiring/circuit breaker/fuse branch circuit.

For the input, your series fuse rating for the panels is probably 15 amps--So at the most, you need 4x15 amp = 60 amp rated wiring (and circuit breaker if you wish). I don't know the Vmp/Imp of your panels, but you should probably have:

Imp*1.25 = minimum rated branch circuit wiring

To:

Isc*1.25= another maximum rating needed
Imp*1.56 = maximum needed to satisfied NEC (or 60 amps, which ever is smaller).

There is NEC which talks about derating charge controller input:

60 amp rating / 1.25 NE derating = 48 amp maximum input current--That I don't believe is needed (personal opinion--If the mfg. of the controller did their job, the controller should be rated for 60 amp input current and not need a derating).

Note that you can choose to run two panels in series (assuming Vmp-array is OK with the charge controller). This would let you use much smaller AWG wiring for the solar array... The down side, is that the MPPT charge controller can be quite a bit less efficient with high Vmp-array and low Vbatt (i.e., Vmp-array>>~30 volts and Vbatt~12 volts). That is your choice.

Of course, you can use NEC wiring specs (temperature, conduit fill, etc. deratings and different insulation options)... Or you can even use Marine specs. which are much less "conservative" than NEC. (you can get even into more details... Marine "SAE" wiring gauge is a slightly smaller diameter than NEC/NRTL spec'ed gauge).

In the end, as Westbranch says--This is your choice. I like to be conservative. Solar/Generator Battery charging is maximum current for hours at a time--Not many of us really use that kind of maximum current loads/ratings in our day to day residential/commercial life. Being a bit on the conservative side usually will cause you less headaches down the road.

-Bill