We replace an old xray by new one, the old xray is fed out of 80A breaker in 400A MLO panel - 480V/3PH. We changed the 80A CB by new 125A CB plus feeder size per vendor drawings. We have only 15 days to finish design per owner's request. Which is the best way to satisfy plan reviewer if he asks for load calculation? We don't have much load information for existing 400A panel or existing as-built document. I know metering is another way to do but code requires 30 days of metering or something like that rite?