I have 2x Wilson Six.One Tour racquets. Both are strung @75lbs. I've played Pro Staff 6.0s & nCodes for >15 years, always @75lbs. without issues. I have noticed 3-5mm cracks on both Six.One racquets on the flat beam @approx. 7o'clock position. There is a silver cosmetic line, & the cracks are...