The problem with all of Petrie's measures is that he only measured the base casing...not the actual side angle.
Easy to determine the height using trig, but the actual angle of the side at the apex is not that as quoted by Petrie.
Compare the peak from any photograph to the peak formed from Petrie's measures...big difference.<<
Do you have any proof of casing blocks having a considerable smaller angle? If this is not the case and the pyramid had a smaller angle then the casing stones would fit in perfectly -they would not be smooth. Also he did not only measure the detached casing blocks but also as he says "the direct reassures by goniometer and level on the granite in situ". To be honest I don't know what "measurement from plumb line" means. Anyway for you to be right we need to know the exact dimensions of the truncated top, it's exact height, and also the width of the casing blocks at that height. Do you have these(especially the last one)?