Wojtek - it's hard to see in this set of pics but the last set shows the stretched sprue added to the mold to give that raised rib detail. Waiting for the brown paint to dry, then I will show pics of the rib paint detail. Then will come a transluscent coat of tan to replicate the clear doped linen look. I do not see any stitching or seam covers in any of the pictures. I know that WWI combat types had this feature, but don't believe this to be the case with this bird. The replicas had the upper covering glued to the ribs only.
Terry - thanks for the compliments, after doing a few, I have that distinctive prop shape down pretty well.