Very difficult to say how much a shaft weight change or flex change will affect the ability of a player to move a ball one way or another. Probably does have more to do with how any change makes a club feel to the player and how that change may affect the way the player swings the club. Generally speaking many have thought that more flexible could make it easier to turn over and stiffer less, but that is rarely the case. Hitting a draw or fade is completely dependent on the club path and face angel at impact and the player controls almost all of that. A shafts contribution dynamically is hard to measure, but again, from a feel standpoint, it could make the difference.
It seems that you should try something closer to the PX weight and mid trajectory profile if you want to maintain the same feel and ball flight. The KBS Tour Light is 20 grams lighter and more of a mid/high trajectory in the stiff, so the profiles are not similar. Again, not sure how much that has to do with what you’re experiencing, but they are noticeably different in profile and weight.
Britt Lindsey