Swing speed - shaft flex conversion

[BritBoy]

I play golf with a friend that is a 30 handicap. He hits the ball well but I think he needs a stiffer shaft to gain accuracy. He is hitting his 9 iron 150yards with reg flex shafts. Does anyone know any info as far as swing speed or shot distance that translates into shaft flex?

He doesnt believe me and is the kind of guy that needs proof before he will do anything.

Thanks

[aquacooled]

well if were talking about shafts for just irons he still should get his swingspeed clocked with the driver anyway. Different shafts has a different flex profiles some Stiff shafts are as soft as regs flex from another company or even between models of the same company.. However if he is hitting his 9 iron 150 yards then yes that is a good clue that he should think of getting fitted for shafts for his irons..