Thanks guys.
The rigging was "invisible" thread, which is a thin mono filament type. Holes were drilled in the wings, the wing surfaces facing each other were finished, and the model assembled.
The thread was then anchored at the inner end, and after that the loose ends were threaded through the holes in the wings, tension held on the threads with clothespins or alligator clips. The ends of the threads were CA'd at the holes, then nipped off close after they dried. They were then sanded and finished on the top of the top wing and the bottom of the bottom wing.
Great sport -- although I haven't built a really tough bi-plane since!
Ed