First invisible thread I used was Coats and Clark and had nothing but breakage. YLI works fine in my Pfaff, either in the bobbin or on top. First I do trial stitching runs on a quilt sandwich using the backing and top fabrics and batting until I have the stitch length and tension I want. May in Jersey
PS. Like the idea someone posted about unthreading the invisible thread into an ashtry to get the kinks out, sounds like a good idea.