I string for my son who is in H.School varsity team (myself a 4.5 level player). Racquet is Microgel Prestige MP (not pro version). Used to string with mains Luxilon BB Ace 18 52lb & Gosen OG sheep 17 @ 54. He never broke strings a year ago when he did not hit vary hard (due to age etc). Now he breaks the crosses at the sweet spot in a few days (10-12 hrs) of play. Moved to PSG in crosses with same mains (BB ace) broke it even faster. Would like to keep tension @ 50m/52 cross. Any suggestions on crosses to keep the same feel but make the string job last longer. Son's 16 and hits pretty solid.