It is a main topic. For what I know from Yahoo forum is the constance with which @kitefreak advocated soft wings vs rigid wings, developping Mothra https://www.youtube.com/watch?v=HE7QDJR7RcA.
Scaling better is also a mean to optimize the land/space use, another potentially main topic.
There is a Storm Dunker’s paper on https://www.researchgate.net/publication/290775361_Ram-air_Wing_Design_Considerations_for_Airborne_Wind_Energy then click on request full-test blue button.
Page 532: “The development originated as an Advanced Concept Technology Demonstrator
research program from Natick Soldier Systems, whereby iteratively heavier
weight requirements were levied (0.25 ton, 1 ton, 2.25 tons, 4.5 tons, 13.5 tons, and
finally 19 tons). The wing sizes were 36 m2, 102 m2, 250 m2, 350 m2, 900 m2,
and 1,040 m2, respectively.”
Now waiting for Dave’s precisions about quasi 2D flexible kites, and quasi 3D rigid wings, their respective potential and so on.