The 'style' or profile of the bow has to match the material. Osage can excel at many different profiles, either flatbows or ELBs, but most others can not. That's why osage is so prized as a first string bow wood... it's versatile. Yew, for example, excels at narrow profile, stacked & rounded belly shapes. However, a white wood, like maple, does not. In other words, it's best not to make a narrow D profile rounded belly ELB selfbow from maple. Maple performs better with a wide flat limb shape. For bow designs, I suggest you read the TBBs, especially Vol 1 and Vol 4. They have excellent chapters on bow design and performance.
As far as the pure physics of the designs are concerned, a wide flat limb will spread the compression and tension forces of the bending equally across the entire flat surface of the wide flat limb shape, where as a narrow stacked D profile belly concentrates the force at the apex of the profile. So, in other words, a second string wood, like maple, will survive as a bow wood if you spread the force over a wider and flatter area.
Have you noticed FG recurve limbs and compound bow limbs? Yes, they're wide and flat. That shape is the most efficient, but not always with all wood bows, like yew. You can make a nice flatbow out of yew, however. All said and done, if you match the design of the bow with the appropriate wood, you'll get the best performance.
