Id uses a scale to figure actual breaking point. I use 8125thin and it advertises 140# tensile strength but actually breaks at 52# on average. Use roughly five times your bow weight in string strength 50lb bow use six strands string, the actual number would be 5 strands but I round up to the nearest even number for Flemish but leave it as is on endless. If you are building a Flemish you might have to double center serve and pad the loops to 14 strands. With an endless you’ll need to either use thick loop serving or double serve the ends to protect your tips it might not be necessary depending on your bow.
Larry