It almost seems like you have two questions in regards to tying with twine ( or Butchers string )I frequently ty the ends with string.This is going to be a little tricky to explain.If you are tying one end to hang such as a salami or summer sausage that is the typical diameter and straight , lets say 2and a half or 3 inches in diameter and a foot to a foot and a half in length ( as apposed to a ring ) you can re enforce your string ty by first tying the usual way then fanning out about one to two inches of the end of the casing and tying that off with a couple of loops and a strong knot so that half your fan is separated from the other half. You will never have a problem.Just be sre your string is long enough.
If you are tying something like ring bologna at the ends together try first tying a common knot around the end of the ring. Ty that tight. Then take a little of the excess casing that you have tied , make a loop and ty that off so your string is tying the excess to itself. Picture a letter U or a horse shoe. If you ty 1 piece of the U it can slip thru because of shrinkage bad ty or what ever. But if you ty both of the Straight arms of the U together it is almost impossible to come loose. Then ty your seperate ends together with more than one knot .
The question i think i saw was what would happen if you were to ty the casing after it was filled to define length.and hang .If your sausage is packed very tightly and you tried to ty it off without there being any "give" it would probably break . When i need to do it that way , I i have the string lying on the table , the i decide where i want the ty.I use my thumb a nd forefinger to make a slight separation , that is where I ty. To be honest , I wish I was good at the twisting thing , you know , where they spin it and it comes out perfect. I am lousey at that. If some one can help me with that please do. Happy SM. Weisswurst