The stock shaft's themselves are very strong.. its the splines in the yoke that are the next weak link if you can't break the shaft itself then of course its the u joints then the rear.. As far as carbon fiber.. I wouldn't really trust a carbon fiber shaft in any drag racing situation as they don't twist they fracture and tear just like any other woven material.. NOt sure how much it might take to twist it.. but me leaving at 6K is not somthing i want to trust w/ anything but a chromoly shaft or a steel at the minimum w/ a loop of course.. Choose your poison...

 

Derek C twisted his apart in his nearly stock '02 SS, and I don't mean at the ends, in the middle, it biscuit tubed apart. All he was doing was starting a power brake on his A4, and BAMBAMABAMABAM, it came apart at ~1600RPM's, the wheels had just started to turn. It had 2100 miles, and 2 months later dyno'd 341rwhp, 358lbs-ft.

I'll stick with my steel for a while after seeing that...