A backing lamination can be either flat sawn, rift sawn or quartersawn. I prefer quartersawn and especially rift sawn myself, but flat sawn will work as well. The disadvantage of full quartersawn wood, is that the medullary rays in the oak are exposed on the entire width of the bow, which seems a bit weak to me. Also, any tiny pin knot will span the entire width of the bow in quartersawn backings, again weakening the wood.