Cleveland Launcher shaft stiffness advice

I just tried a S-flex demo of this model and was very impressed. I always thought (and have been told by club fitting pros)that I should be hitting regular shafts but here was no R-flex available. I was also told buy the sales guy that they are 'true' R and S-flex shafts. I have a smooth swing and hit a 7 iron about 150yds and my driver 250-260. If a shaft is too stiff, what would I expect to see in the ball flight? How about too soft?

If a shaft is too stiff, you'll probably notice a week shot to the right (assuming you are right handed)
However, if the shaft is too soft, it depends as to what your normal ball flight is. Most people think that if a shaft is too soft, it will hook. But if your normal flight is a fade, a weak shaft will exagerate the fade, maybe slicing.