I did some work on the elevators. They are a little crude and the areas that need more attention are marked with red pencil. I hope to work on that today. When they are ready I will start with the three planes.
Although one normally wouldn't start with the tailplane, I think it was a sensible decision. This way I can gain experience for the enormous wings. I ordered sheets of 1400 x 1000 x 0,5 mm styrene because this is what I will use the most. These big sheets are ideal because the span of the model is 120 cm and the 4 wings have a length of 57 cm (without the central part). I really have to think ahead how to handle this.
I have enough material to experiment with. As advised the core will not be of balsa. I have some different sorts of wood. It will have to be light, stiff and easy to shape. Maybe I can reinforce it with fiberglass rods or aluminium u-profile. Or maybe a brass support frame including incidence and dihedral. If I do that for both the upper and lower wing, the cabane struts will have to be reinforced too because of the added weight. (Solid lines would be brass.)