Swing Speed and Shaft Flex

So Crossfield does an experiment where one of his highly skilled mates hits S and X flex, there isn't much difference so he concludes that flex doesn't matter. I look forward to the follow up where he gives a X100 to a 15 handicapper with 75mph 6 iron speed. I wonder if that will be any different from the players own club?

We have known for some time that good players have a greater capacity to deal with equipment. If you give Rory a set of Dunlop Jessie Valentines (ancient cheap ladies club) he will still knock it round in a decent number but if you give me Rory's X flex driver and PX 6.5 or 7 irons, I won't.

In other videos Crossfield has said that the head design doesn't make much difference. Now the shaft makes much difference. I presume when you go into his shop he just tells you to pick the prettiest set because it doesn't really matter.