Got any pics of this stave? Ash can vary greatly in density from tree to tree ....anyways,if you lay your width out right you can make a 1/2" mark at the fade from the edge of the back down the side and a mark 3/8" from the edge of the back at the tip and facet a line...and reduce down to that line,but not erasing it like you normally would for any other bow...that's if your just making a normal flat bow style of bow ....that will get you into floor tillering every time for normal hunting weights with any kind of wood except yew n junipers...just as long as your width lay out is correct