At NASA 1958-1964How Flexible Is Flexible?
In his 1967 presentation, NASA Research on Flexible Wings (rre-08), Rogallo explained that tests were conducted with different types of structural stiffness, from “thin sheet metal” to “all flexible”, with very different results in performance and simplicity of use.
Most of the data on flexible wings are on configurations having rigid leading edges and keel, and the sweep angle fixed by a spreader bar, or by a very rigid apex.
The parawings have nothing to do with Rogallos’ kites. They can certainly not be considered as flexible wings. “Rigid-framed membrane wings” would describe the parawings more accurately.