Reference the wing sails, hang gliders have been double surface for a very long time. It's not rocket science.

You can fold an 36 foot wingspan glider into a 18 foot by 1 foot tube that you throw on top of a car and then throw into the garage.

I'm not sure of the state of the art in design, but when I last flew, my glider was about 20 minutes to rig and about the same to derig. I believe that it's considerably faster now with the new designs.

Most gliders had the ability to vary the geometry of the sail with some sort of pulley or lever. You could spread out the wing thus tightening and increasing the span giving better high speed and flatter glide. Loosening the wing gave better landing characteristics.

A hang glider is considerably more complex than a sail, as fractions of an inch in sail shape can spell the difference between a docile machine and a rocket ship from ....