When I smooth out the back, I treat it like there are no knot. I'm looking for symmetry with these bows, not following growth rings, dips or rises in the wood. I'm talking about your typical pin knots, not huge loose nots. If it's a sold knot, up to a half in or so, and probably larger, they have never caused any issue with any yew I have worked. Since these knots will only be on the belly, they cause no issues, even if they are on the edge.