Hello,
Thanks for the clear explanation.
I found on the internet a numeric illustration of your theory.
For BKT tires 7-16, 8-16 and 9,5-16 the rolling circumferences are (sorry : in mm) 2217, 2360 and 2542.
So the difference between 9,5-16 and my present tires 7-16 is 325 mm or about 12,8 inch...