I hit the U510 4 iron only with the smoke shaft that feels dead in my opinion. 88-90 is my mps. I play a AP1 4 and 5 iron, 6-PW AP2. All with the TT XP 95 which is my favorite shaft since years. Compared to the AP1 4 iron the U510 is few yards longer and also very forgiving. Has anyone trying different shafts like the Tensai blue or others? I play this shaft in my TS2 hybrid.