Your 437.5 unit has thrown up some more curiosities which you may have already come across, but I'll pop that in here too just in case.
When it is applied as a multiplier to the 1.728 and 1.8 cubits you get 756 feet(GP side length) and 787.5 feet. 787.5 is quite close to 792, a familiar canonical number. The difference is 4.5 feet(54 ins)
This turns out to be a divisor of 792,( 4.5 x 176), which you are no doubt aware is John Michell all over, so 792 and 787.5 are the two variants of 175 and 176 for the module of 4.5 feet.

756 is also divisible by 4.5= 168. The difference between 756 and 787.5 is 31.5 feet, which is itself a divisor of both in the ratio of 24:25. 31.5 feet is 7 x 4.5 feet.

If you apply 4.5 feet to the sarsen ring it throws up 99 feet at 22x and 103.5 feet at 23x. 103.5 is quite close to 103.68, another familiar canonical number, the difference is 0.18 feet(2.16ins) 103.68/0.18 = 576, with 103.5/0.18= 575. 99/0.18=550.

Curiously I have come across 4.5 feet as a measure elsewhere and I've been wondering about it ever since because it seemed out of place. Now it makes much more sense.

I must admit that 437.5 is a new one on me.

I find the canonical system is a kind of thread that underpins all sorts of other similar systems, much like the ones you are exploring here. There seems to be a relationship that ties them all together with the canonical as a kind of datum core for the others to hang onto. Since I started looking at things this way the notion of figures not quite adding up isn't such a stumbling block. I now think that near misses are more likely due to an as yet unidentified spur off the main stem which will come to light sometime in the future, just like the 4.5 feet has here when combined with the 437.5.

Your insights have opened a door there. Thank you.

cloister