This thread reminds me of a Cobra driver with a Fuji Ventus Velocore (red in color), reg flex. Weight was 50ish grams. Well, needless to say, it was too stiff for this old man. I let some of the young Turks hit it at the driving range. These guys pretty much hit their drives 300 yds or so. They all guessed the shaft was a stiff flex.
Bottom line, I sold the shaft and got a Fuji Vista pro in reg flex. Much more my speed👍