The present invention relates to a release film comprising:. A foaming resin is sandwiched between molds so that a hollow blow-molded foam having a ventilation path is molded, and a fluid for use in cooling the hollow blow-molded foam is allowed to flow through the ventilation path so that the hollow blow-molded foam is cooled. Accordingly, the developer may then provide a generalized testing regimen to test instances of product provided by a vendor, identify those containing the flaw, and may optionally provide a solution to the flaw, where practicable.