"In virtually every grade the basics of Alchemy are presented and taught to the student of our order."
from The Study of Alchemy page of the Esoteric Order of the Golden Dawn's website
After putting so much effort into fine-tuning the coordinates of the significant Ripper locations, I assume that I've nailed them down as precisely as I can with the information at my disposal, and I'm back in the business of looking for patterns, angles, sunrise dates, alignments, etc.
Now that I've started to get nitpicky about the details of the Ripper pattern, I'm beginning to think that the peak of St. Paul's cathedral, not the east end, was meant as the reference. It just makes more sense from a surveyor's point of view, and the dome of St. Paul's is the ideal point from which to observe and measure sunrises. (For millennia, temples have been precisely oriented to the sunrise at certain times of years, and this has helped archaeologists determine their ages because of subtle variations in sunrise patterns over long periods of time.)
I decided to look at the McKenzie location first. Using the Movable Type Scripts bearing-calculator, I calculated its bearing relative to the east end of St. Pauls, and came up with 6.65 degree. I did the same using St. Paul's dome-center as the reference, and got a result of 6.39 degrees, which is more interesting because 6, 3, and 9 are key "occult" numbers. It turns out that surveying equipment even at the time had an accuracy of about 30 arc-seconds, i.e. 1/120 of a degree, so it's possible that 6.39 degrees was the intended angle. It would be simple to place McKenzie's body at the precise location along Castle Alley required to produce this angle. Also interesting is that this corresponds to the sunrise on 9/6/1888. I also noticed that there is an angle of 96 degrees (6 degrees below the east-west axis, corresponding to the Rose Mylett location) and of course the one at 15 degrees (1+5=6) to the Ada Wilson location. So, there's the requisite triple 6 (rotate the 9 in 96).
I looked for alignments, and I noted that the "ray" passing through the center of St. Paul's Dome and the McKenzie location seems to bisect the angle formed by Whitechapel and Commercial, and that it lies on top of a road named Ben Jonson Rd. way out by the canal to the west of Mile End park. I also looked for anything else of significance, including on old maps, and noted on the old maps that Ben Jonson Rd. had the same name at the time of the Ripper's rampage.
So, I went to Google Earth, and drew a line precisely between St. Paul's dome and Ben Jonson Rd, and was stunned at how close it passes to the McKenzie location. It seemed possible that there was something to this, so I converted the name to its numerical equivalent, and came up with 3 6. Still, this didn't seem especially significant, so I Googled the name, and found that Jonson was, according to Wikipedia, "an English Renaissance dramatist, poet and actor. A contemporary of William Shakespeare, he is best known for his satirical plays, particularly ... The Alchemist...."