Shaft Fitting

Knowing and looking at the wrong shaft measurements, that's one thing.
Knowing and fitting with the wrong shaft measurements, that's something.

For instance, if you are 180 lbs, you will likely choose a 75g shaft, with a regular 200g head + 50g grip, that gives you roughly 320g club at 45", a SW that's around D2/D3. Average people feel this is the most stable combination, meaning that you can drop the club in the "slot" and produce optimal club-speed. Some people with different weight, choose heavier or lighter club according to physical strength, and together with feel, this is where trial and error comes into picture. Though, you can only perform trial and error after you have a narrowed scope.

As general outline, flex could be fitted by swing speed, torque could be treated as a sign of forgiveness and release in timing, weight could be paired with strength, length could be adjusted according to height and finally swing weight and the shaft's characteristics, are varied by personalized preference. Noted that indicators like "tempo", "rhythm", "hitter or swinger", "1 or 2 axis swings", etc are normally not used as they are more a swing mechanism but has nothing to do with shaft fitting.

U.S is always an unique place where different circumstances allowed to happen, I meant those extreme scenarios beyond the norm. Only in U.S you will find shaft of 55g and X-stiff, take a look at other branded Japanese shafts, you will never find this combination. The argument behind is in order to go for extra distance, you sacrifice the stability for faster swing speed. This makes sense as U.S is a country of raw power. Though, do you perform better when you increase swing speed, do you hit longer or better? Normal understanding says you have to give up one to get the other. Yet, does increment in swing speed proportional to increment in distance?

The other view to look at this is, do you want shaft deforming for optimal performance? is deflecting in shaft shape a parameter to the swing's tempo, meaning that your tempo determine when to place the shaft back to the initial point that it bounds back and release all the energy on the ball?

So simply put, there are many measurements in shaft fitting to be considered, but fitting depends on how one prioritize the parameters grouped and chosen. (e.g. weight and length, then flex and torque, then SW). Usually the most charming fitting is the best distance under the controlled dispersion, providing that the golfer himself is assumed the fixed variable. An understanding view to this would be a sliding bar where left is swing speed and right is control, you choose the best fitting parameters available to move the slider horizontally along both ends, finding the optimal setting. Yet, you could never have both ends together.