Michael,
I have another one of my crazy ideas of how to duplicate the rippled plywood sides, but it will take a number of steps. Since the sides are relatively flat, it shouldn't be impossible though.
This is a variation on the technique I used on the Pup wings. I noticed the same wrinkles appear while building the wings if I didn't use enough heat on the shrink wrap.
1) Build a side frame from scale basswood, the kind used for model RR. Figure out the dimensions from the model and photos, of course.
2) Get some shrink wrap. I have the perfect kind, I'll send you some. It took me a number of tries before I found the right kind so I'll save you the leg work.
3) Super glue the shrink wrap to the side frame as you would and old stick and tissue kit. Don't stretch it too tightly at this point.
4) Here's the tricky part. Use a hair dryer (borrow your wife's since I know you have no need for one usually

) and gently shrink the plastic, but not too much. As it starts to go tight, the wrinkles will appear as in the old W.12 photos.
6) Spray paint "Future" or some other varnish to "freeze" the wrinkles in.
7) Now make a silicone mold and cast in resin.
Yeah, I know it sound complicated, but I think the results will be worth it.

George