This may have been posted before, but I am reading his book now and he talks a little about his stringing preferences. over 70lbs with 17g nat gut! page 110: "On clay, I strung 32 to 33kilos. on grass, 32kilos; on some fast hard courts, I went to 34kilos (74.8lbs). Because of the thing string and high tension, the gut sometimes snapped at crazy times....one year i went through more than 700 sets of gut."