Best Practice for running 8 DC home run cables through roof to combiner box below

I have 30 solar panels in 4 strings and 8 pv wires I need to get from the top of a 12' tall picnic shelter with metal roof down about 6 ft to go into midnite solar combiner box. I want to drill 2" hole in roof with black rubber boot. can I just put a couple of elbows on top to prevent water from getting in to meet NEC code?
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