I used nyltex and it was ok, then I bought a spool of Barbour's 7 cord and it is much better. I wax it myself with "sticky" wax, beeswax with rosin mixed in. The Barbour's is 781 yards and cost me $65 shipped from Landwerlen Leather, 317-636-8300. The wax I got from Bingham Projects Inc, 801-399-3470, $2.90 for a 1 oz cake, 3 shipped cost $10.40, they call it "string maker's bow string wax". It takes more time to wax your own but I think its worth it. I use Osborne harness needles 0 size, 517-0, 18 ga 25 in a pack was $5.75 also from Landwerlen. If you get the white Barbour you can dye it with the leather dye, I bought both black and white.
I have also used some Maine thread waxed cord in the .035" size, needed hot pink, worked well but if I get more from them I'll go up one size so its closer to the Barbour 7 cord.
I also tried some linen from somebody else but it doesn't even come close to the Barbour's linen.
That's what I know.
Jeremy