I recently switched from 3-pw Taylor made Forged Tp with Dg s300
to
5-pw Taylor Made R7 tp with the 6.0 project x shafts
I was concerned about the firmness of the 6.0 Rifles
and it turned out to be a non issue for me . The club / shaft combination seem to fly the ball a little higher across the board.
Actually a little off the subject, I actually replaced my 3 and 4 iron with the Adams idea replacement hybrids partially because I was afraid of the stiffness of the shafts and it turned a weakness 185-215 yardage into a strength.
Long story short all I noticed was a slightly softer feel and a little higher ballflight 5-pw in the project x 6.0 shafts
good luck