| Barkley said: ok from the multitude of high quality size comparison images available now I've deduced the following. |
If you are calculating with 305mm length, you get the wrong surface size of the side and therefore also the wrong volume.
It is a rhomboid/parallelogram, not a rectangle. So you have to multiply the height with the length of the upper (or lower) edge (~275 mm), not with the total length (305 mm). Geometry is fun!










