Took my trusty Burner 3 wood regular flex to see what all the "hoopla" about the RBZ is. I'm 60 years old and hit my Burner 3 wood about 210 yards. I hit 10 balls on the monitor with it and averaged 208. Hit 10 shots with an RBZ regular shaft...averaged 228. Hit 10 shots with an RBZ STIFF shaft...averaged 237 !!! The pro told me that although my swing wasn't exactly calling for a Stiff shaft, the monitor showed a more penetrating ball flight still going right down the middle with the stiff shaft.
Bottom line...walked in hitting 208...left hitting 237.
I am a believer.