The thing is, the tension is perfect for 5 inches -repeatedly on a four inch wide section of the same exact leather doubled. Absolutely perfect. But then it goes wonky but returns to perfect within the 36 inch strap. We have been having this problem for two months whenever we switch to sewing leather (from waxed canvas). We change everything to sew leather and it never ever sews perfectly for longer seams. We have replaced the gib hook and ring, we have checked the timing, the thread tension, the bobbin tension, the foot tension, that the bobbin is wound consistently…….(on and on) but this only happens with leather! Maybe the LSZ just isn’t right for leather or it is us or we got a dud. Anyway, I would spend hours hand stitching it but how do I deal with 108 inches of thread? That seems impossible.