I have always used what thread the dealer suggested for me to use on my Bernina 1530 which was Mettler Silk finished 50 weight thread. I have recently tried Aurifil 50 weight thread which also produces an excellent stitch. My baby refuses to let me use less expensive thread such as Gutermann or C&C. I don't know why you want to use a heavier thread. I piece and quilt with 50 weight thread with no problems. Good Luck in finding a solution.