Don't over-think this. The Pete-n-Poke is a flat bottomed airfoil. Press a yardstick up under the wing and see where the other end lays in relation to the horizontal stab. Zero incedence would be parallel. Whatever the distance between wing and stab is would be the radius. One degree change would be (2 * radius)/360, so adjust the wing so it ends up by that measurement lower (with the model upright.