Wow, what a fascinating post, Bruce! You kept my attention.
I never realized 4' Clarions might break back and will have to keep an eye (or an ear) out for this. I always assumed reed ranks transitioned to flue pipes. Possibly the "Clairon-Doublette 2'" at St. Sernin cemented in my head the idea the incorrect idea that high pitched reeds transition to flues, as night follows day.
I rather fear that I have not adequately explained that (Willis) Clarions, where they broke from reeds to flues, continued at 4ft pitch and did not break back to 8ft.