I have been considering re-shafting my irons and have watched a number of You Tube videos which showed the frequency matching process using a frequency analyser. The builder then checks the cpm’s against a chart to make sure it agrees with the build instructions for each club. But what I don’t understand is “where does the design frequency come from”? I understand that during the fitting process, a number of different shafts are tested and the one that best fits the golfer’s swing is selected. If irons are being fitted, is it only the 6 iron that is tested and when the best shaft has been decided upon, is it the frequency of that shaft that is used to compare where it falls within frequency ranges for L,A,R,S, and X stiffness? For instance, if the best 6 iron/shaft choice indicates that it falls within the middle of the Regular stiffness range, it would mean a cpm of around 310-314(I think). And for every other club, you would be trying to get a cpm pretty well in the center of the Regular range. Am I correct on this? I look forward to any response.