The understanding of prototyping has changed in recent years to an approach that accompanies the product development process and therefore plays a vital role. Decisions on prototyping activities are not only taken selectively but throughout the entire development process. To consider this, the author has analysed classic product development strategies concerning their suitability for planning prototyping sequences. Based on the results, a hybrid planning approach was presented. The core of this approach is a criticality assessment of the functional areas for the prioritisation and planning of prototyping activities. This paper examines the applicability of this propagated approach using the example of the development of an additively manufactured cranial remoulding orthosis (CRO), a conservative therapy for threatening positional plagiocephaly (PP) for infants.