Hello Cladking and all,
As far as can be determined, from the upper end of the lowermost block down to its lower end the Ascending Passage narrows in from the sides by a total 3.4".
The lower end of the first of the blocks (which is tapered to fit the Passage narrowing) is only 15" from the roof of the Descending Passage, and that last 15" is surrounded by partially unsupported limestone.
My concern with these three blocks being allowed to travel freely down from the Grand Gallery to the bottom of the Ascending Passage (a disquieting 150 feet or so) is that you end up with a battering-ram effect that might easily have sent the first block loosed bursting out of the Ascending Passage and into the Descending Passage.
Comments, anybody?
MJ