Just a thought. If you want to make a balsa canopy, and I understand why you want to do this, you have to carve the outside to the shape and style you want. You are pretty much there to where you have a plug. You could then pull your own canopies, and/or use the plug to lay up a fiberglass or carbon canopy that might be lighter, since you are counting grams?? Something made from 1/2oz glass would weigh almost nothing.
Type at you later,
Dan McEntee