David,
Thanks for your reply in both tone and content.
As for the tees on the 10th hole, there were 5 tees in 1924 (I have a 1925 photo that shows the current back tee), 5 tees in 1930 and two tees were combined prior to 1934 resulting in 4 tees. Today, you can see the remnants of the short tee that is no longer used. It probably didn't work very well for weaker players since the hill up to the fairway is so close. By the way, the landing area in the fairway just past the left bunker is exactly the same elevation as the current back tee.
The 18th tee was very small in 1924 and 1930. In fact, for a time it may have been maintained as the smallest tee I've ever seen by Flynn. You can see the remnants of the tee on the ground today. I think it was correctly measured. The back tee prior to the 505 yard tee put in for the 2005 Amateur, was lengthened to its current yardage of 463 from the middle of the tee for the 1934 Open. What do you think the elevation change is between the 1930 back tee and the edge of the quarry? What about the change from the tee to the landing area?
The information needed to conclude yardages is in the Flynn book. Though not yet published, a number of people have copies of the manuscript. Our sources of information were found in private collections, including Merion GC (its research library and archives is open to the public under certain limitations) but much of it came from libraries, historical societies and other easily accessed public sources.
Since you are not comfortable with my assurances or Tom Paul's confirmation, nor are you patient enough for the Flynn book to be published, I suggest you come to Philadelphia and see for yourself.