Ogy: First of all. Petrie measured the Menkaure pyramid and found it square.
Now. In my previous post and calculations I made a mistake and didn't double the square at Menkaure's.
SC: G3 is not a square. As I explained in a previous post to Don, the Giza Plateau Mapping Project (led by Dr Mark Lehner) was the most recent survey commissioned on the plateau. Alas, however, it has never published its results. Dr Lehner, however, tells us:
Menkaure's Pyramid was named 'Menkaure is Divine'. Smaller than his predecessors' pyramids at Giza, it has a base area of 102.2 x 104.6m (335 x 343 ft). - Lehner, Dr Mark, 'The Complete Pyramids', p.134
I am not sure how you come to your figures but I guess treating G3 as a square as opposed to a slight rectangle may be part of it. I defer to my own results which show that it is entirely possible to create three bases from the Belt star asterism whose orientation, order and proportions agree with that of the Gizamids to an extraordinary high level.
I have created a new presentation (here) of this which offers more visual information of the geometric relationships between the Gizamids and their 'queens pyramids'.