So we are working out our system to build giant-scale planes on a budget. We build mostly our own designs. It is far more challenging to wing it. I have to say that building from forms is pretty challenging, and worth it for those of you who like to do it their way.
One suggestion that I have for you guys is, lattice. Maybe that is not an obvious description. We have the most luck building complicated curvatures, when we lay out a regularly spaced net of 1/16th inch (1.5mm) balsa strips x 1/4" (6mm) . The spacing is what ever makes sense for the model. I mean, you will need to work out some of this for yourself. We find that wings are good with 6"(15cm) pieces cord-wise and 20- 25% spacings span-wise. That way there is a reasonable pitch and still a good amount of coverage. Onto this, you glue your actual skin down. This helps reduce the actual curvatures involved, but also allows for the skin to be supported without the need of a foam internal block. Use wood glue if you are working on a Styrofoam base or CA if you are working on a compatible base. CA will eat Styrofoam, even the vapors will destroy it.
We get all of our balsa from local suppliers. Our favorite supplier is www.solarbo.com .