I made a spy pistol crossbow today. First build ever, I think it came out pretty well But after about a dozen shots the material I used to connect the therma-band gold ruber keeps breaking. I have even resorted to using picture hanging wire (7 strand - 12kg metal wire). But that still breaks too. I'm wondering what is the best material to use? I have seen Joerg use paracord, but I can't find any that is 1.5mm thick. I need something strong and wear resistant. Would bow string work?