I followed Ray Rimmell's example from his build in Windsock Vol. 26, No. 6, by using extra linen rib tapes from another WNW kit, after the first color coats had been painted. I glossed, applied the decals, then added another light coat over the decals. It is subtle, but visible.
On the underside, I went from the tail up to the "V" where the curved fuselage meets the wing center section, then from the leading edge of that section to the nose (except for the cross brace for the landing struts). It seemed logical, to me, to not include the "flat" area under the wing, not having an actual photo of that area at hand. I did slightly miss the "point" of the V, which wasn't noticed until long after, but not going to redo it now.
Rich