I have been using the stuff to make egglofters. Egglofters are models that launch eggs as high (or as long) as possible and still get the egg back unbroken. Eggs are heavy, weighing in at about 60 grams, so the weight of the model is at a premium. Eggs are not very streamlined, so a shroud to streamline the egg shape is also at a premium. Enter the Kapton. Egglofters tend to be shaped like an ice cream cone. The egg is encapsulated at the ice cream end with the parachute right below inside the cone. The cone is made of a sheet of Kapton curled to shape and held together with double sided tape. The pointy bottom end is cut off just enough to allow an engine tube about 3/4" in diameter to stick out. The fins are glued to the engine tube.
The Kapton is considerably lighter than the card stock that is often used for the cone. The difference in mass can make a 100 meter difference in altitude for a model launched with D impulse engines(20 Newton-Seconds).