It proved to have similar performance to contemporary standard class
gliders.Some advantage in efficiency being generally lost to handling
induced inefficiency. So - There was no compelling efficiency
advantage.

It should be noted that most all hang gliders are flying wings. The
reason for this has more to do with portability than with performance.
The handling quality of many hang gliders since, say the early '80, are
quite pleasant - remember, this is weight shift contol.

Tony V