The technique I liked (recommended in the GP CAP 232 .40 kit I just finished) was to wet the sheeting with alcohol (I used 70% rubbing alcohol from the drug store) and let it soak into the balsa. This softened the fibers making it much easier to bend around the formers. You then use masking tape over the balsa sheet to shape it to the formers or ribs and hold it in place. When the balsa dries, it will retain the shape. Then use medium CA on the formers and carefully pull the sheeting down onto the formers and hold it for about 30 seconds. You can add masking tape to hold it until the CA fully cures. I suppose you could also use this technique with wood glue, you'd just have to hold it in place longer.

Brad