Almost everything is rated for 75C these days and putting in 90C terminations on both sides of the long run is trivialIt's not really a derating, it's the calculations for current and wire ampacity in the PV section of code. We are still restricted to temperature limits of 110.14(C)(1) that keep us using the 60c column unless we are dealing will connectors and equipment that are rated for higher temperatures, So unless the inverter, disconnect, and all connections in between are rated to greater the 60c you gotta use the 60c column.