My findings are broadly in line with just over 70 mph reached, and the drawbar/coupler forces seeming to be low.
While I am still not convinced that the figure for the steam used by the cylinders at any point in time is correct, I have been conduction a series of tests at different cut off rates and comparing the ITE for the shown OR cylinder steam rate with the 8P test Willans lines Graph 48. I am finding that depending on cut off, there are two things which do not fit the lines. The Willans lines start at 20mph and depending on the cut off, OR is probably giving more ITE than Willans shows up to a certain speed, at which point OR provides less ITE than Willans lines show. This crossover point is at a higher speed as cut off used is lowered. At 20% cut off the changeover point is around 20mph, but for 15% cut off this point is between 40 and 50 mph. The variation appears to be between 2000 and 3000lbf lower for OR than the Willans lines suggest. Difficult to say how much higher ITE is being provided at lower speeds as the Willans diagram does not provide any curves for them.
For instance with 35% cut off, using 33,643 lb/hr steam at 40mph, OR is providing 17,365lbf ITE. The Willans lines for that steam rate and speed show about 20,500lbf.