There is a small aircraft historical society in Oregon that has a geodetic fuselage hanging their building. I can't remember if it is Player's Plaything or one of the other's mentioned in Powells article. If close it would be a good resource to study. Look up Oregon Outlaws.
Go to an engineering library with a reciprocal arrangement with your local library and check out a copy. Be very careful leaving it too close to your scanner. You could suffer electronic osmosis of information on to your hard drive.
One of Flying magazine's Aftermath columns was about the GP-4. Garrison spoke with Mr. Pereira who verified that some of the flying qualities required experience to deal with.
Darrol Stinton has a book on flying qualities. That might provide some guidance. Also look at the NACA tech reports on...
Wonderful! Between Drew Fidoe, RS Hoover and the above references you should be able to test the material to see what strength it has. Then you can head down to Ace Hardware for a $7.99 container of certified Weldwood and you are on your way.