Before anyone carries on with opinion and words like "baloney", may i politely suggest that you go and read David Myrha's excellent book, The Horten brothers and their all wing aircraft- published by Schiffer.
Given that the Horten brothers were part of the book and okayed it for Myrha, you can take its contents as definitive.
Having had a long term research association with their work, I think I can say that there use of early plastic, plastic -type coverings, allied to wooden and steel tube construction techniques, was mostly due to the needs of weight, range and the unique function of teh flying wing.
In case you do not know, (and it not in the book, but it is published) a Horten airframe that was "resecued" by the USA in May 1945 as part of Operation Paperclip, was taken to the USA and later tested for its glide ratio. Sadly it was modified by those that thought they knew better, and the unique bell shapped wing lift distribution pattern was ruined by the mods to the canopy and centre wing area. Having done that, the Horten was then slated for its poor performance...
gents, if youa re going to slag the Hortens off, do try adn do your research first or you will end up lloking very silly.
And it is no coincidence that the latest UAVs and such blended wing desings, resemble 1930s Horten designs. Check out the 60 degree swept Horten glider that the F111A Stealth fighter resembles.
Try the "nurflugel" web site too...for part of the story on-line