Keep in mind that any aircraft design is a conglomerate of theory and compromises. We go with what works well in theory and if the airplane flies well we attribute that to a successful theory. The fuselage needs enough side area to perform knife edge well. My theory is that if you need to fly the fuselage more then 5 degrees positive AOA then you start getting non linear control cross coupling. This means that with rudder you also get roll and pitch. Reducing the rudder amount you need to fly knife edge loops keeps that couple to a minimum. With older designs you would need a ton of rudder throw. The problem with that is even with TX mixing you will never quite match your mix to the couple unless you have a TX with multi point mixing. This is why you see taller and taller fuselages. It's also why you see some monoplane designs with the small wings behind the canopy.

The position of the upper wing on my design was pretty well thought out. There are structural and aerodynamic reasons behind it. Traditional Cabane struts would have added complexity and a reduction in strength. The wings depend on one another to stay intact. The more important reason is the separation between the two. Farther apart would increase lift efficiency due to the lower wing getting less downwash from the top wing however having the drag of the top wing farther above the thrust line creates a whole new set of issues. Trim change with speed change in both horizontal and knife edge flight being the bigger of the bunch. So the upper wing gets what we call " shoulder mounted ". The canopy position is fairly important too. You want to have side area balanced fore and aft of the CG. This helps keep the airplane from weathervaneing too much in a cross wind. A well proportioned airplane just requires you bank the wings slightly into the crosswind to hold a line.

As of now the fuselage on my design is fiberglass/balsa sandwich composite. The wings and stabs are traditional balsa sheeted foam. I am toying with the idea of full composite.