Remove the sapwood layer that is directly over the heartwood and all the rest can stay where it is. (And if you figure out how to do that, post a build-along!)
Del, Bryce, Weylin, and Coaster gave you the real story about reducing sapwood, but they forgot one important point....POST PICS as you go! Lots of us have no yew to play with so we have to get our thrills vicariously.
Good luck, buddy!