Don't know anything about swings, or much about clubs and shafts for that matter. I can only describe my own experience knowing that my swing, at least when on, hasn't changed much in 20 years. 20 years ago I was playing Wilson Gooseneck Staff blades with DGR400 shafts and my stock iron shots were a boring and very controllable trajectory. I liked those shafts enough, that I built component sets with forged cavity backs and the same Dynamic Gold R400 shafts, and both of those launch the ball on a notably higher trajectory. I don't know how much difference the shaft makes since I didn't put different shafts in any of these heads, but the blades definitely went significantly lower with the shafts than the cavity backs do. The cavity backs were TP Forged that I bought from LowProGolf, and Alpha C1 Pro irons that I bought used in the FGI swap shop.
