I would think it would be better to put the larger wings under the front or middle closer the the payload/center and have the smaller wings in the tail? Why would these designs do the opposite?
With the first (DAPRA's X-plane) you can see the weight is going to be put properly under the bigger wings but I also wonder: why have it fly with the smaller wings infront? If a teardrop shape is the most aerodynamic then the big wings should be in the front. Also it looks like a having the smaller wings in the back would increase stability in flight.