Hi Massimo, hi all
I play with RF97A since the beginning, and with other 340/345g Wilsons before that, but RF97A is very different from those other frames. My strings in RF97A don't last much, 2-4h maybe, but I hit hard. It is a particular racquet, and I've learned a lot over the years.
Roger was asked "speed or rotation" and he instantly exclaimed "Rotation!", and beside more rotation he wanted significantly more power from his new 97 sq in frame, so that he doesn't lose overall speed when giving a lot of brush on the ball. RF97A is stiff, that provides power, and torsionally stiff and stable, with slightly wider string spacing for more rotation on the ball. So not exactly ideal for flat hitters, because its stiffness is compensated with rotation - or more precisely - string snap back. That means mains sliding on crosses when you hit the ball with some rotation. Roger even uses low friction material string savers between gut mains and ALU crosses, so that gut slides more easily over the crosses. That sliding of mains provides significant softness and give on impact. Gut is exceptionally elastic and soft, and is like that all the way until it breaks. If you string gut in mains and ALU in crosses and then hit completely flat with full power it won't feel soft, because gut isn't sliding on the crosses to provide softness and shock absorption so you'll feel mostly ALU, that can feel brassy or boardy in a stiff frame. So you need some rotation for snap back. That is why you can easily see Roger always attacking the ball with rotation on those slow motion videos on yt, and why statistics say that players with most rpm on the ball are 1. Rafa, 2. Roger. When the ball dips and jumps "into the nose" of the opponent it is significantly more difficult to return than a flat ball, and if you're Roger approaching the net, you'll get a higher volley as well.
If you use poly strings, even stiff ones, but that provide great snap back, it will also work great. It will be controlled, and not boardy nor too stiff. However, most poly strings are slick and slippery only when new. Well known examples are RPM Blast with its silicone coating that wears off in 20 minutes, Revolve and Revolve Spin, Poly Tour Pro and most others. When they lose their coating after 20 minutes they lose most of the snap back and then it feels too stiff and sometimes boardy. You can try and compensate with a softer tension, to get more snap back, but RF97A is a stiff heavy power frame, and if you string it too soft you will definitely lose control. Balls will fly out, and you'll find yourself forced to spin to keep them in. Strings that I found best to keep their snap back, sliding and tension are Head Hawk Touch and Head Lynx Tour, but they do require some harder hitting. Hawk Touch works really great for me, definitely best trajectories when hitting 100%, all the way until it breaks. I string them at 27kg/60lbs, but both Hawk Touch and Lynx Tour are control strings and can easily be strung lower. For players who want poly but aren't hard hitters I'd suggest Isospeed Grey Fire, slightly softer than other two but still great. And Hawk Touch is actually made by Isospeed for Head, both are Austrian companies.
As for Luxilon ALU, 4G or Original, they give a stiff-like crisp feel, and can feel too stiff if you're not hitting hard enough. Many modern racquets have stiff hoops, that makes them string sensitive, RF97A is also like that. Best example are Yonex Vcore Pro 97's, they really don't like higher tension with poly. I'd definitely suggest Luxilon Element for crosses, I personally use Hawk Touch on crosses when I string gut on mains, and that combo really lasts a lot, Hawk Touch keeps the slick mantle all the way, so it doesn't saw into the gut, and feels less brassy or stiff than ALU but provides total control like ALU.
I definitely agree with the comment that you have to correctly play with your whole body, mass and legs to play with RF97A, excellent comment. You have to anticipate the incoming ball, always, always. The frame is heavy and very demanding, so it instinctively makes you think about your swing/arms, so you forget the legs/mass/body, but instead you should "forget" your swing/arms and think about your legs/mass/body to play nicely with it, which can be counterintuitive.
Also, it is super well dampened, and I would really be surprised if you got an injury or soreness from RF97A. The weight and some aramid fibers in the layup, both help a lot to absorb vibrations. Different other frames gave me tiredness, injury and soreness but I always return to RF97A to feel good again in the arm and shoulder.
@USPTARF97
Yesterday I just installed new grommets on my 2016 black RF97A's, but not original ones, those were out of stock for years it seems, but these new ones, intended for this new v13 paintjob. The product code number is different too. They fit perfectly, are 1g lighter, 23g old vs 22g new, which I like a lot, since my RF97A's are 3g too heavy in the head from the factory (343g). It was never a particular problem since I mostly use 1.25 strings (17 grams) but when I string 1.30 strings (21 grams) it feels sluggish. I compared them in detail, and they are identical, only the silver "W" insert on the bottom on the side is very slightly different, a completely negligible difference. Even the polymer material seems identical. I bought 6 so I'm happy now.
