As far as wood choices, the FAA gives various woods the OK for certified birds if they conform to the MIL spec. In one of the FAA publications, it gives the specs. I used certified Sitka spruce for my wing spars, and locally bought Douglas Fir for most of the rest. I ripped it to size. I got to prefer the European plywood over the US plywood the more I worked with it. Mark Goldberg Austin TX