>But since when did it become known that the pyramid sides are slightly concave? Post 1925 would seem likely, and so Cole didn't take this factor into account!. <

Are you suggesting that Petrie didn't know about the concave sides? If you are you are wrong as he wrote about it in "The Pyramids and temples of Gizeh".

>This hollowing is a striking feature; and beside the general curve of the face, each side has a sort of groove specially down the middle of the face, showing that there must have been a sudden increase of the casing thickness down the mid-line. The whole of the hollowing was estimated at 37 on the N. face; and adding this to the casing thickness at the corners, we have 70.7, which just agrees with the result from the top (71 ± 5), and the remaining stones (62 ± 8). The object of such an extra thickness down the mid-line of each face might be to put a specially fine line of casing, carefully adjusted to the required angle on each side ; and then afterwards setting all the remainder by reference to that line and the base.< "The Pyramids and Temples of Giza" First Edition Page 44 (This paragraph is ommited from the second edition)

Jon

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