help me with shaft flex!

[jamesj]

ok so currently i have a cleveland launcher 460 ti (2005 model) with 9.5 degree loft. the shaft is the default reg flex 55g (gold color). i bought this off ebay without ever trying it. i originally tried a 2006 launcher at a demo day with an aldila nv shaft. i forget the flex but it may have been regular. i loved it at the demoday and bought one off ebay. ive had this driver for 9 months and its been decent. i can hit good drives off it sometimes. today i hit two drives that were 280+ but i have to choke down on the grip and swing at maybe 70%. when i swing as fast as i know i can under control, it will slice. everyone that uses my shaft calls it a grandpa shaft and wiggles it around like a wet noodle. now im starting to realize that maybe it is a little too flexible. im 21 years old, 6'1" and 190 lbs. and i go to the gym everyday (can bench ~300lbs) so it occured to me i may need a stiffer shaft. i haven't been fitted but i went to a proshop where they had the system where you can hit balls and a screen shots your ball flight and speed and everything. i didn't measure my swing speed but ball speed was ~160mph and the guy said my swing speed is usually 70% of that. he watched me swing a few times and said without a doubt i need a stiff flex shaft. so is the flex shaft the cause of my slices? what shaft is good? ive been looking at the aldila nv-65 stiff shaft.

[limpalong]

Virtually impossible, today, to recommend a specific shaft without seeing your swing. Your narrative, however, does give credence to the fact you need a stiffer shaft. Is the NV the correct shaft? That's where the guessing comes in.
If you have a smooth transition, you may want a shaft that isn't really tip stiff. If you are quick in your transition, then a tip stiff shaft would be better.
A graphite shaft that has too much torque (too flexible) will allow the clubhead to "lag" open with a faster swing speed. So, the flexible shaft in your Launcher could well be the reason for a bannana ball. Does this mean a stiffer shaft will be the magic wand for your slice? Not necessarily. A reverse pivot, a body that gets out in front of the hands... there can be many causes for a slice. Anything that prevents the clubface from closing can be at fault.
Find a driver with the NV in that you can demo. If the NV in stiff flex seems to feel good and cleans up the left to right, have one installed. I will tell you, it seems folks either love or hate the NV. Not a lot of middle-of-the-roaders. I've tried 3 or 4 drivers with it and can't feel the love. My son-in-law... with a really hard swing... loves his NV in his G5. Again, find something you can hit quite a few balls with and see how it feels to you. Good luck!!!!!