20.61111r stands out like a burning sun to me, i have posted on the boards about its importance.
The relationship to Petrie's second determination is cast iron being 20.6111r x 160/159 = 20.740740r and you have to look at Jacob's work on this cubit length.
If you use my ideas re cubit design and also base 100 design the cubits fit together like glue with emerging relationships that are now becoming apparent within the GP design.
The cubits used at the GP are produced using 100/4.8 where 4.8 is fixed and 100 is variable so cubit x 4.8 gives proximity to 100.
Cubit x 1200 gives Earth circumference in miles and cubit x 1760 gives GP base in inches where the solar day is 100 inches.
This is bolted on to the 1760/280 or 44/7 framework.
The 1760 is also a variable but is fixed in my model.
20.611111r x 1200 = 24733.333r miles against base 100 of 25000 miles difference 266.666r miles = 1408000 imperial feet
20.740740740r x 1200 = 24888.888r against base 100 of 25000 miles difference 111.111r miles.( Berriman's 10/9)
Based on the evidence produced by Berriman and yourself you are going to have to go some to argue these are not the intended cubit lengths that align with Petrie's evidence for both determinations.
20.6111r x 160/159 = 20.740740r
I am saying the proximity to 100 will produce these cubit lengths as fractions of 20.8333r the base 100 cubit
20.611111111r x 4.8 = 98.9333r/100 x 20.8333r = 20.6111r
20.740740r x 4.8 = 99.555r/100 x 20.8333r = 20.740740r
This is a provable theory working with every cubit length you will ever come across.
I know with a probablity amounting to a certainty that this system will also produce the measures identified by Professor Alexander Thom at Stonehenge.