There is no certification board. You as the builder of the aircraft are responsible for using appropriate wood that meets government standards. This means clear, no knots, no runout in 4/4 over 20 ft with a minimum of 6 rings per inch. So if I could get 5 rings per inch with some wavy grain over 20 ft to use as gunwale stock at a reasonable price I would buy it. My 1937 OT CS was not made with super duper spruce but it wasn't bad either.