You should have enough to split or saw it in half lengthwise and make 2 staves. If you do saw or split it in half I would clamp each half to a form or board to prevent twisting, warping or taking too much reflex or any deflex. Or better yet bind them back to each other with spacers between the 2 halves to allow air circulation. How thick is the sapwood? I wouldn't worry about the crown eitherm although with yew you can violate the sapwood to achieve a more uniform back.