I'm trying to put some info together for a 600 Amp 120/208 3ph service. All this info pertains to the service wires which extend from the POCO pad mount XFMR to the metering cabinet, then to the OCPD. My plan is to run parallel runs of 500kcmil XHHW Alu. I have a few questions. Do I have to derate for 4 conductors? I guess I'm not 100% sure when to add the neutral conductors for derating. Let's say I'm required to derate, then I derate to 80% which gives me an allowable amperage of 280A ( 90 degree column = 350A x .80= 280A). With parallel sets that gives me a total of 560A. Am I able to use the rules from 240.4(B) which would allow me to go to the next size circuit breaker ( 600A) Any help would be appreciated. Thanks