Mussie: That's for faster, and doesn't account for changing airfoils for the purpose. For example, a 747 has a better glide ratio than a Cessna 172 (17.7/7.5).
As you get big, the flying wing shape really shows its benefits because you are getting rid of induced drag. If you needed non-wing cargo areas, something like a canard setup might be effective too, because that's an example of an aircraft that balances on two lifting surfaces instead of having a lifting surface (wing) and a downward pushing surface (the H-stab) fighting it out the way a conventional layout does.
Heck, when you get real big, why limit yourself to monolithic structures? The F-16 example (purely as an exercise, it would hardly be practical) could even work if you wanted if you designed it so that each plane remained free of the wake turbulence of the others. A hundred feet of carbon fiber rod between each wing and smart enough coordination to keep it together is an intellectual excercise that shows the limit would only be financial, not physical.
