OK I goofed. Every "restored" Canadian Chipmunk I have seen has had an all metal wing, so I assumed they were built that way. I just checked my copy of, Canadian Aircraft since 1909, published by Putnam. It states "The single spar wing had a stressed-skin leading edge forming a D-spar while the rear portion of the wing was fabric covered"
Sorry to lead you down the wrong path, now I know something about Chipmunks I didn't know before.