
(Just to avoid confusion, I'm the original Andrew Wood, not the Andrew Wood 6 who started this post)
I also had an r5 Draw, stiff shaft (for exaclty the same reason!) and am a serial slicer. Tried the NV reg in my r5 - no benefit. Suggest something much softer should be tried, such as the NVS, Prolaunch, YS6+, in reg flex (agree with the comments about stiff = worse).
Ultimately I never got my r5 working with any shaft, except when I really worked on technique. Problem was that it was a 9.5° - too little loft, too much side-spin (as someone said above, it's all about spin rates). You might get more benefit from going to a very low-spin ball (I found the Wilson Staff with those weird, flat dimples really made a difference, esp. the Px3)and it's cheaper than a new shaft.
Be careful before going down the new-shaft(s) route - it's long and expensive and you may just end up junking the r5D (it doesn't fix a bad fade/slice) for something with higher loft etc anyway.
Good luck. And remember that the r5 is a .350 diameter tip and needs an insert-ferrule (counter-sunk hosel) if you DIY it.