Making flying things lightweight is a means to an end, not the goal or a hard requirement. Makani experimented with a wide variety of solutions before settling on their final model. The initial work on soft kites had serious durability issues, IIRC. What they ended up with looks a lot like a very lightweight airplane, for good reason.
[Former Makani software engineer, here. I wasn't involved in the early stuff, or the design trades, but I heard a lot about it.]
[Former Makani software engineer, here. I wasn't involved in the early stuff, or the design trades, but I heard a lot about it.]