What is the current thinking on fitting clubs with the proper shaft flex, other than going for an analysis of your swing which in my case probably changes from day to day or month to month(my swing speed is 80-90mph). Is there an advantage to using the proper flex for your swing speed. Many of the newer shafts even in the stiff range are actually very light and and swing speed may be enhanced. What are the problems incurred when using a shaft that is either too whippy or too stiff ??Is it a feel thing or does the moment of impact change.