I had acquired a 72 inch long, by 2 inch wide, by 2 inch thick stave of black walnut. It is straight, clean, and I decided to decrown so I could back it with either maple or hickory. The thing is, the stave is all sapwood. I would like to make a bow out of it that is 66 inches to 68 inches long, 1 and 3/8 to 1 and 1/2 inches wide till just past mid limb where it will taper from there to 5/8 or 3/4 for the tips- similar to an eastern woodlands profile. I would also like it to be in the neighborhood of 45 pounds at my 27 inch draw, and I am thinking of a semi working handle. My question is this, How does black walnut sapwood differ in compression as compared to black walnut heartwood? I know that trapping the back may help some, but any design/construction tips for what I am looking to get out of this would be a big help. Also, are my two options mentioned above for backing good ones, or would there be something better?