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No pics to prove it, but I saw 16 or 20 degrees downhill in Pittsburgh, PA last Christmas. That was fun, and I got to prove that Hill Descent Control works as advertised!
13 is the max I saw as well, it was at a state park in GA. Had to go up and back down the same hill. Was on a road though so it doesn't really qualify.
I've seen 18 or 19deg up/down, I think steering is maxed at 34 or 35deg, and I managed to get a shot of a recent trip that brought me to a 23deg side tilt.