I have a pair of yew billets spliced that look to be mostly sap wood with only small pin knots here and there. I was able to avoid any big knots.   The billets were already decrowned when i acquired them so they are basically boards. What would you recommend for a backing?  I have hickory, bamboo, silk, linen, flax roving, and sinew ready to go but could make up some quarter sawn ash, birch or elm as well. Thx for the advice.