I am about to build my first small pv system consisting of 4 100 panels in 2s2p arrangement, a PowMr 60 amp MPPT solar charger, an SOK 12 v 206 Ah battery and an existing modified sine wave inverter to drive hydroponic lights . There will also be a 12volt output for an Icom IC7300 transceiver. I will have a circuit breaker in the pv line, and one between the charger and the battery ,and and for the 12 volt outlet. there will be a 150 amp fuse between the battery and the inverter, but no switch. The circuit breakers will be mounted in an ip65 clear cover power distribution box with din rail and a bus bar for the lower current negative connections. Is there any reason to use double pole circuit breakers rather than single pole, and can I fit 3 breakers in a 6 position box? Later expansion would be to go to 24 volts with 2 SOKs in series and a decent true sine wave inverter.