Hi Pushboater,
We used hickory for our stingers. Its properties make it both tough and pliable. As a result, none of our stringers are kerfed. The cost was in the range of what you might pay for pine. Hickory is a hard wood and needs the right size pilot holes for screws. Otherwise, the screws will simply break, and hickory will laugh you to scorn.
Here's another picture, taken from the opposite direction.