Multiple wings mean a lot of drag and center of gravity problems. There are reasons airplanes look the way they do, it isn’t like a million alternatives haven’t been tried.
“Multiple wings mean a lot of drag and center of gravity problems. “
CG is only a problem in the vertical axis. i.e. CG is well below Center of Lift. However, fore & aft (longitudinal) and side to side (lateral) center of Lift vs CG are very well controlled.
One problem, depending on the method of propulsion, will , in getting the enter of trust and the center of drag (parasite & induced) close. If a prop is used (ducted fan) placing the Prop shaft the top of the roof looks about right and would allow a large, slow turning, quiet & efficient prop.