[Bicycle Bob]

I have considerable experience with inflatable displays, and they always are assumed to leak and require a continuous air supply. Some idea of the possibilities can be found in the hot-air balloon contests. Given a chance, an inflated structure will look as much like a bubble as possible. Cones are easy to produce, but cubes are hard. For a flat panel such as a fastback rear window, some extra structure is needed. Ribs can be added by using separate small-diameter tubes inflated to fairly high pressure. The nicest realization of this is made with two tailored layers separated by deep ribs, much as a really high-quality down sleeping bag is made.

I would favour a lower structure that would curl up like a New-Year's noisemaker to stow the whole inflatable tail in a neat roll at the bumper. It might be necessary to mount the taillights and licence plate on tubes that telescope from the belly pan or roof, and follow the tail in and out.