Today, I strung up my leaded extended O3 Red with 15L Prince Tournament Nylon mains and Monogut ZX Red 16 crosses. I manually pre-stretched both (added about 1.5% to nylon relaxed length, and about 7% to ZX relaxed length). I strung at 75/50. Initial observations. 1. Hoop is only squashed 1/8". O3 frames are better reinforced in the string plane - this is less squashing than a conventional frame for this differential. 2. The mains move and snapback freely, but the crosses are pretty much locked in place. I look forward to trying this out on court.