Not sure if this has already been posted.....
This video seems to show the opposite. The 850 appears to be pulling away from the 800 the entire video..I was reading in the mountain section and someone posted that the 850 got the jump on the 800 going up a hill every time no matter if the 850 rider was heavier or not. They went on to say that the gap established at the start did not increase. It remained the same diststance the rest of the way up.