I learned with my BL Quilter's Choice that it helps to have the tension a little loose on both top and bottom. See Jamie's Wallen YouTube on adjusting the bobbin. The reason is due to the speed of 1500 stitches per minute, so the looser tension helps the thread move more smoothly with the fast moving needle. I check my tension each time I change the brand, thread weight, etc. I upgraded to a mid arm machine recently and still keep the tension same as before.