These may help:

http://www.tpbweb.com/media/catalog/404.pdf

http://www.tpbweb.com/media/catalog/412.pdf

http://tpbweb.com/media/catalog/611.pdf

Try to find and use A-grain balsa.

It seems to me that bending a 2-3/4" wide x 30" long piece of 3/32" balsa sheeting (less than the sofest type) is not easy task.

The formers and the stringers are not the most solid surface to achieve a nice round C shape.