I string my son's racquets, who's a 14-year old national tournament player (UTR 10). We use Solinco Hyper-G 18 in the mains (currently at 51lbs) and Babolat Origin 17 in the crosses (54lbs). (The crosses only last about 4 - 6 hours, so I stay busy). I used to string them at the same tension, but...