white ash makes a great backing for woods like red oak, walnut and ash itself. sometimes hickory just isn't needed. ash backed red oak is my favorite other wood combo. Its also important to remember that Marc St louis chases a ring on ash before making into a backing for yew and hhb. I have always just used a good qtr sawn board. As far as a backing for white oak, i think linen or silk wood be a better choice.