What's a heavier string? Let's say 1 inch of a 12 strand ff string for example? What's going to weigh more, 1 inch of 12 strands with no twists or 1 inch of 12 strands with 4 or 5 twists? In my mind when you un twist the 4 or 5 twists in that 1 inch of string, it'll be longer than 1 inch meaning more material and more weight. I know it may or may not be that big of difference....everyone has done their own testing but there are so many variables in testing its hard to say....but a lighter string will mean a faster arrow. But if you want an easier time tuning a flemish is the way to go. Heavier strings will absorb noise and so will the twists. I personally like to work to perfect some things so that's why I like wood arrows and endless strings because once you get them right there isn't anything better...that's just my opinion.