I don't know if I am just imagining it, but I recently had my Cab 20 re-strung at 21 lbs. about a month and a half ago and it already feels loose. I do hit very hard and have a very fast swing, so would this cause my tension to go down so quickly? It feels like its only at 18 lbs now. Should I string it at a higher tension to compensate for this drop? Also, off topic but, are tennis grips suitable for a grip?