I have used 1/4" ash successfully as backing on several cherry bows, very nice shooters too. But its too light for hickory, maple, walnut or american elm, it would probably work on hackberry or red elm as they are less dense woods like cherry. By the way ash makes a pretty good bow by its self too, or with a hickory backing. Hickory backing is not too picky about being perfectly straight, you can usually get away with a few run off grains in the working area, unless you are trying to make an elephant bow.