I take it you are talking about the very fine nylon monofilament thread, I use this stuff a lot, both on the top and bobbin. I wind my bobbins very slowly as it is so stretchy, and only half full. I don't alter the bobbin tension as it's almost the same weight as bobbin thread. 80 which is cobweb fine, I use the large size, 68000 metres as I find it invaluable for so many things..
Here's a link to the stuff I use, nylon monofilament
I also use the mid weight one weight 250, but for toys etc as it can be scratchy, that I buy in 10000 metere spools.
You need to make sure it does pass through all the tension points and behind the thread guides. I find a net handy to prevent it spooling and use a 2.5 mm stitch length, for zigzag between 3 and 4 millimetres width and a 1 millimetre gap between the stitches. My top tension I reduce exactly as I would for satin stitch, and I stitch moderately to slow to prevent excessive thread stretch.
I love the stuff, and contrary to the scare stories you read about it melting, as long as you don't use a cotton setting on an iron it's fine.