At 5.1-5.2 pH, it should stretch really well, 5.4 is too high for it to stretch properly imo. From my experience, lower pH results in better stretch. Mozzarella made from water buffalo milk stretch better with a pH of 4.9-5.0. Make sure to do a stretch test on a small piece of curd before proceeding to heat and stretch all of the curds. The test curd must stretch over a feet easily.