Need advice here. My son got his first full-size racquet (Wilson UL100) last year, and the pro shop racquet specialist, who saw him hit, set him up with Wilson Revolve, I think 17 gauge (I didn't know enough tennis to state a preference). When we got the Revolve cut out, a different stringer, who knows my son, strung it with Luxilon 4G, 16L, at 57 lbs (!) . However, recently I've read several articles warning against using poly for a younger junior, and I wonder if we're putting his arm at risk unnecessarily. He's never broken a string in his life. He is good for a 12 year old and has decent topspin, but his arms are skinny-tiny, no muscle to protect those tendons. He plays against teens with more powerful forehands than his. He says he likes a "crisp" racquet feel, where the ball doesn't sit on the racquet for long, and he plays with no dampener because he likes the feedback of vibration letting him know if he hit off-center...would he lose that crisp feel if I switched him to something more arm-healthy? He has great control with his current set-up but seems to have to work hard to get power. He will probably play on our town's excellent high school team in a few years, if that makes a difference. Thanks in advance!