To make wings for actual model aviation, you want as low a density as possible, so a BIG single-wall print is probably optimal, as long as it holds together.
This model has been made with interlocking bends so as to make assembly easier.
Edit! The second file (modularwing2) has modified geometry which should allow it to pass 45-degree spec with NO INFILL which is probably preferable!
For this you'll need to get two things from Skeinforge: a satisfactory strutting on the slot/tab connections, and removal of the top and bottom caps. This way, the wing will pass 45-degree spec and hopefully still be as light as possible.