Sketch of an elliptical kite balloon like the Allsopp Helikite constructed with a rolling heat sealer (on left).
Jeffrey Warren and I discussed these kite balloon designs when I was at his studio. Southern Balloon Works, where a lot of spherical Grassroots Mapping balloons come from, makes a similar kite balloon with a drag rather than lift structure for stability. John Borden of Peace River Sudios loaned me the roller sealer. I showed Jeffrey, he found one for sale at retail, and Dan Beavers found an online store that sells roller sealers.