There is also an interesting discussion on these matters at:
From there (Some small parts of text have been changed, not to repeat everything posted there):
Well, thinking CE marking is not conceived for racing boats, but for the recreational market, where most of cruising boats are short handed and boats should look after their crews, in my humble opinion, I think it's worrying that some boats can be labelled as Category A, taking into consideration they have what has been commonly understood for many years, among designers, NA’s and boat owners, as 'cruel' and even dangerous ratios and parameters. Those boats are too stiff by all means, with a low motion comfort ratio, too high accelerations (And so quite punishing for a short handed crew) and with Capsize Safety Factor well above 2, widespread considered a safe limit.
In my opinion STIX provides not enough information about the seaworthiness of a boat (It was never intended to be a clue to this, but this idea is spreading around quickly) and may even be a tricky and dangerous number. Seaworthiness is a complex matter, involving stability, all around scantlings, quality of movements, and a long etc.
I think manufacturers/designers should at least be obliged to publicize the STIX Factors and not only the number itself (Which is not even mandatory!). And even better, publish also the 'old' ratios and parameters, for the people to have a more complete view and understanding of the boat.
Rolf Eliasson (One of the fathers of the STIX number) himself expressed some serious concerns about the STIX number and how it finally 'came to life', in the aforementioned article. He even suggested minimum STIX for Categories A and B should be 40 and 28, instead of 32 and 23 as it is now. But even rising the level provides not enough guarantee as to define a boat as seaworthy, as we could see per numbers above.
Again in my opinion, most probably a great pressure from modern mass (and light) boats producers (and their designers) was put into the process. Those manufacturers produce very nice boats for Club racing and coastal cruising in fair weather (what most of users do) and fun to sail, but of course they want not many of their models to be obliged to be labelled as Category C, what they should be in most cases.
Long range racing is quite a different thing (with full trained crews aboard), than family oceans crossings so, in my opinion, CE Category's assigning criteria should be revised and adequate to the RCD’s own reason of existing. If racing is intended, a new special Category or Note should apply in addition to the ‘familiy’ Category.