100.8 feet is a commonly quoted figure for the Sarsen ring mid-diameter, by the likes of John Michell and Robin Heath for instance, with 97.32 for the inner dia. and 104.28 for the outer dia. I have seen alternatives but this is the one that seems to work best for me, but as I have already said I believe the Canonical(simplistic) is a kind of datum that other similar schemes are attached to, so other similar diameters that work with those other schemes would also be part of the greater scheme, in my opinion anyway.
I no longer see all this as having to fit one rigid scheme to the exclusion of all others. The Canonical does seem to tie everything together nicely though, as you've shown in your pyramid calculations there. Very curious how it jumps parameters like that and still works perfectly. There is something a bit otherworldly about that.
288. That's an interesting figure. It has come up a lot in my scribblings, especially regarding Stonehenge.