No doubt your company's product design engineers are using something like 2% extra length to account for stranding assembly.
1) - Check to see what excess calculation the product design engineers are using now.
2) - For each product, check to see what excess length (scrap) is left on each pay-off reel. (Compare to the length on the beginning of that same pay-off reel to learn what you believe was left over.)
3) - Statistically collect the data for a good period of time for each product so that you can determine if the extra length allowance can be reduced.
4) - Discuss those results with the product design engineers.
5) - Run experiments with reduced extra length to prove your theory.
6) - Have the product engineers modify the extra length standard accordingly.
Be very cautious about this.