Duane,
It's a pretty new design so I haven't messed with different taper yet, I may try more taper on the next on have been using .002 taper up till now. I have used core tuff and it doesn't hurt performance that i can see. I'm getting between 178 and 186 fps on average with 10gpp arrows with this design. I may try messing with stack, taper, and materials to see if I can get a bit more out of it. Oh yeah they shoot pretty darn well too.
Cory