To Clarify, I mean that the Ezzy way of combining masts may not work for other brands with different sail design and construction techniques. It clearly works perfectly for the Ezzy sails which are designed around these combo's.
With all masts the top part has more bend than the bottom part. Also, as you go shorter the IMCS flex tend to get softer. My assumption is that the smaller bottom section would make the mast combo more Constant Curve biased and the smaller top section would make it more Flex top biased. However, since this is an 'indexed' mast system, I am not totally sure. I may have to do an IMCS test on some combo's to find out.