Lowest no gunsmith scope mount?

[Maxwell Smart]

I have to hand examples of the B-Square, S&K, Accumount, Fultons and Armalon no-drill scope mounts for the No 4 rifle.
I test fitted them all to the same Long Branch No 4 Mk 1*, with 1" scope rings.

Found only 5mm of difference between the highest to lowest.
Lowest was S&K (S&K rings) C/L of scope 51mm above C/L of bore
Highest was B-Square (Leupold .730 low rings) 56mm above
The others lay in the 52-53mm range, so there is not all that much in it.
I am only trying to fit a 20mm objective scope, so am using low rings only.

Other factors such as allowable ring positions, to suit position of scope turrets and eye-relief will come into consideration.