I just ordered a new set of the AP2 714 irons with PX 6.5. Current Muzuno MP59 with S300 and all of my shafts in my woods showed up in super slow motion as being to weak and prone to hook.   Changed to better shaft in driver and and my teacher, who teaches three PGA player, said the numbers were perfect.   PX shafts are consistant and a bit stiffer but not as stiff as X100. I have found these shasts to produce better flighting and very straight shots.