seasons greetings and thanks for the kind and knowledgeable words. Hugh franklin and i have been working together for quite some time now and his work on the GP is not as well known as it should be. He has mentored my work and anything I post about the GP has his signature all over it.
i am very aware of the unit you post as 39.375 inches.
I have suggested that Michell's 'Canon of Ancient Measure' is based on a scaled circumference of 132000000 feet and this is against Jim Wakefield's unit of 1320 feet ( incidentally the length of the lesser cursus at SH )
So a model as 1000000 units of 132 feet ot 11 x 12 feet.
Using this model your unit represents a circumference of 131250000 feet and this is 750000 feet short of the top of the scale.
It eaquates to 24857.95455r miles very close to the polar circumference but not quite.
Multiplying 39.375 by 64 gives 2520 and this is stade again ann approximation for the polar circumference as 360 x 7.
I would be interested to know how you work this unit with the megalithic yard.