My brother and I are in early testing with the 99S...
Test 1: (before any forum research) Sonic Pro 17g Orange @ 49lbs on a lockout/crank machine. My brother prefers a pretty loose set up and this was too soft for him after one match. It was too soft for me to even bounce the ball around the house. Snap back was totally gone.
Test 2: Sonic Pro 16g Black @ 55lbs on a constant pull machine. Still felt amazingly soft - was okay for one match but it was too springy for me after that. I hit a couple impressive topspin shots but it never really had any magic. My brother still wants to try it at this tension but snap back is already degraded considerably. I knew less crosses would make a differerence but holy smoke.
Might try PHT or Juice 16g @ 60lbs next.
Boris Becker Delta Core Melbourne, Solinco Tour Bite 17 @ 52lbs
Laser Fibre/Stringway ML100 T92