I'm scraping a little each day on my ash stave. It is 70" tip to tip. The handle is stiff, the fades are just under 1.5" and the limbs run parallel for about 18" before tapering down. The final 6" of each limb is stiff, tapering down to about 1/2" for the final 4" with a slight flip at the tips. I draw to just under 28" (27.5 - 27.75 somewhere)
I haven't yet pulled it more than about 15" -- just enough to get the limbs to bend enough to use a tillering gizmo to mark the stiff areas. But I can tell that it's going to be pretty light on the draw weight. Seems like piking is going to be in order to get it in the 45# range. Since I have stiff tips, I won't be losing any working length. But taking it down to 66" or even 64" seems like it would put the limbs under more stress at the same draw length.
So I guess I'm wondering just how far I can push it before I'd need to add some sort of backing for safety sake.