I have found both banding film, the 6" wide stretch film found at the BORG's, as well as torniquets as used by phlebotomists to draw blood, to be great at holding things together until glue sets, especially oddly shaped things.
BTW, all plastics shrink when heated, but only shrink film will stay shrunk perpetually. Lessons learned from a curious mind selling industrial packaging for more than a decade.