With 35lbs of meat on your grill, there is going to be a big temperature variation below and above the grate. It's just like the difference of temps below a heat deflector and above it. That much meat is going to act like one big heat deflector holding heat below the grate. Your dome thermometer will probably read 50-75 degrees LOWER than directly below the meat. Maybe even more. I would recommend turning that meat once every 2 hours or so to get it cooked evenly.
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