Nigel, I don't think that resolving the motion into horizontal and vertical components is really relevant to Gordon's method. He will measure progress along the line of the slope (just like a car's mileometer would). For a given stroke of the "oars" that movement will be the same regardless of the slope. The only problem that the rowers have to overcome is the additional reverse component of the stone's weight. Since they are already lifting its entire weight quite comfortably in a vertical direction the additional slope component is small by comparison at moderate slopes. At 1 in 8 it will be about 5 tons for a 40 ton stone, but this is dividied amongst 40 rowers, so the additional component is only 280lbs per rower. This is further divided by the mechanical advantage of the lever (say 20:1), so it ends up at around 14lbs. On the other hand the brake man has to be able to resist the full force of 5 tons acting down the slope (albeit for a short time). I suspect several brakemen would be needed for a stone of this size. I like your idea of having trailing logs lashed to the stone to act like pawls against the ground. Mr Otis would be proud of you.