I've made bows from hickory and oak that are 70" long, 1 1/2" wide at the middle two feet tapering to 3/8" wide nocks, about 3/4" thick at the grip and 3/8" thick at the tips, bending the full length (D bows)and pulling 70-80#. They weren't heat treated either, though that would have helped. Bearing that in mind, I'm sure you can get a bow that heavy from a stave 2" wide and 68" long. Again, heat treating is always an option.