The straighter the better in my opinion. This aids in overall straightness and string alignment. But you will be able to work with more imperfections in your wood because of a backing more so than with a selfbow. You will sometimes have pin knots front and back on selfbows so having them on just the belly of a backed bow isn't a problem. The one thing you don't want is wood with sever grain run-ups. This makes for an iffy proposition. ART