Another stringing question. Been looking at string patterns and some racquets have 22 main, but others only have 18 main. Just wondering why? All of these racquets have the same number of thread holes, is this to keep the shape of the racquet? Also, the skipped hole is different too. For the newer racquets they all skip B11 Main, but some of the basic models skip B9 instead. Just wondering why this is so too. Thanks.