Pappy - yes, made the second string but I am now shooting with it. It takes some time to test these, because now I can shoot at most 2000-3000 shots per month. Still, after testing this second, two test samples are too little.
Marc - yes, you are right. But how much there is difference for example between 4x and 8x (strength coefficient) strings in durability? 100 % or something else? I really don't know. Maybe I should make 4x test strings too. The only problem is that I can not shoot so much to get dependable results...
But, you raised a very good point about serving tight. According to many old sources too tight servings are problematic in linen string - they can break the string. I make serving by hand, without serving tool and I make them quite tight, which is of course my subjective assessment. So, what kind serving is too tight serving? If the servings are too sloppy, it not good either. How will the string break then, if the reason is too tight serving?