Back in the 70's we didn't have carbon fiber and we used 1/16" sheeting with no reinforcement. We generally glassed the wings with 3/4 oz. fabric too.

I am finishing a scratch Curare with 1/16" balsa sheeting which was pretty light so I used some 3.7 oz. uni carbon, 2 strips top and bottom and I glassed the wing with .5 oz. fabric.

I would say if you use 6-8 lb. 1/16" balsa, you don't need reinforcement except at the center section. If you use 4-6 lb. contest balsa with no glass, I would put something in there if monokoting.

Jeff