The brand of invisible thread really does make a difference and I also would choose poly over nylon. Some types are wound differently and need to be mounted horizontally (embroidery thread spools) and some of the invisibles. If you don't have a horizontal mount, you can try putting it behind your machine in a coffee mug or mason jar to control the lashing if it is a problem. Getting the tension set right just takes patience and some machines just won't play well with the "slick" invisibles.