I don't know the G/S angle for that particular runway, but a good rule of thumb is to multiply the distance in NM with 100 times the G/S angle (which is about 3 - 3,5 degrees for most runways) to get the height above the field at that point.
So that would be 9.5 x 3 x 100 = 2850 feet, assuming the miles you're talking about are indeed nautical miles and not statute ones.
Note that this equation assumes all aircraft are already established on the G/S, which most probably is the case at 9,5 miles, especially the bigger ones. Maybe someone can fill in the blanks concerning the difference in altitude between MAN and your shack, but it looks like the old man is right
