and heat gun often run into three major problems.
One: The shrinking plastic wraps under the plug making it difficult to remove the finished canopy.
Two: As it shranks the neck of the bottle rides up over the mould.
Three: It is often difficult to get the plastic to shrink down over the steep face of a flat fronted windshield.
Here is my method of solving these three problems. It is not perfect, and there may be other ways that work