Is that really due to 'fabric failure' or user failure?

The ones tested were fresh from the factory, Boudi.  I suspect that if you take the factors you have mentioned into account as well, its probably nearer a 25% 'failure' rate.

As for the question about the fertility cycle means of contraception, I believe that the more you take a variety of 'cycle' elements into account, the more effective it is - but its getting accurate 'readings' for these varied elements that is the problem.  Never tried it, mind; just what I remember from reading in various publications from John Hopkins School of Medicine and their pregnancy research department that the Nursing Campus in Pokhara subscribed to (and I had to sort out as part of my work assisting the librarian there).