Matt,
You Should Not Violate the grain on the Back of the stave.
You should lay out the Limb/Tip width to on the Back of the stave to correspond with the narrow limb, then remove wood from the sides of the
Large Diameter Limb to leave the Front profile that matches. Then you remove wood from the belly, passing through the core/pith of the tree as needed
to make the limbs relatively even in cross section.
You don't remove wood all around the circumference of the tree/stave to make the size match.
On some sapling bows I've made, the bow wound up with a channel on one limb, the large end of the sapling,
where the pith was removed. In the other limb, the top of the sapling, the center/pith is still buried in the limb.
-gus