Well… the short answer is, that there is no problem doing what you propose. Both shafts are .355T shafts. But why are you making a move to a regular flex from a rather stiff 5.5 flex? What is your typical 150 yard club?
Going to a graphite shaft, and a softer flex, makes sense if your back issues have slowed down your clubhead speed. Even if you speed has not slowed down and you still need an S flex, graphite can be more forgiving to the body for those of us with back, joint, etc. problems.
Well… the short answer is, that there is no problem doing what you propose. Both shafts are .355T shafts. But why are you making a move to a regular flex from a rather stiff 5.5 flex? What is your typical 150 yard club?