I have the best success when using regular thread in the bobbin. Do a bit of testing to get the top tension right. Some clear or inviasble threads I have to reduce the tension ALOT. some I only have to adjust by a tiny bit. I also use a very small needle in my machine as the invisable thread is thinner than regular thread. Using a top stitch needle will make a much bigger hole than you need and sometimes you will get skipped stitches.