This is way to accurate, but make sure you have a full tank of gas to. Won't that make a difference in the measurement? Mine doesn't look to much different from yours, maybe I don't have as much rake as I thought.
And back seat or no back seat. I just put my back seat in yesterday and that sucker is frickin heavy! And any tools kept in the jeep during measure. Also, add heavy tire carrier and big spare or not and winch or no winch.