Using Buck Converter as Solar Charge Controller ? (see pic)
It's probably safe because it won't likely work as the Buck charger will probably collapse the PV voltage to very inefficient low voltages.
A MPPT controller will hunt for the MPT by matching load impedance to the PV source for any solar condition. Max Sun each PV is Zmpt=Voc/Isc=17V/0.6A.
Also, this block diagram is rather simple and leaves a lot of specs out.