the way to test your machine tension is to sew a straight line on the bias/diaginal: gently pull the fabric fabric by holding the ends of the stitching line. If the tension is even then the thread will not break. if the top thread breaks then the top tension is too tight: if the bottom breaks then the bottom tension is too tight. keep adjusting the tension u til the thread does not break. All that said: I have found that it is really hard if not inpossible to get the tension balance when doing FMQ. for that reason I use matching thread on the top and bottom.