Actually it wasn't the mirror that made me smile.
Cuben fiber is the cloth used for the spinnaker sails of modern racing yachts. It is very strong, light and all that, very techie stuff. It is a carbon and polyester fiber laminated fabric. Carbon for strength, polyester for flex.
Yes, very strong and light, also quite pricey.

And yes it is true the ultralight backpackers are trying it out for tents, tarps and hammocks. (Even though there are still some slight problems with the carbon fibers fatiguing when sharply folded.)

However, I think he would have a problem stuffing it into that small of a capsule, especially when he is talking about using it to fill waste space.

(If he succeeds I want to see pictures, and then I might invest in the idea.)