Badger: "I never let the desired draw weight dictate what the bow will finish at." This is a really good point. Experience helps me look at this or that stave and say, "I can get a low 40's flatbow out of this" and I use the TBB width guidelines and go wider if I can on whitewoods, etc.
But, sometimes I'm wrong. Sometime you have to shorten the stave. Sometimes the wood just feels weaker than it should be, sometimes the knot is worse than you thought. If I'm taking any set noticeable set by brace height or a tad higher, I "manage my expectations" down a bit. If I'm taking none by 22" on the tree, I start to make a longer stiff tip, or narrow the limbs a bit depending on design.