Our research program aims at finding and testing method components for deciding on and implementing organizational splits and mergers. We tested a method to timely detect design & migration issues of a Post Merger Integration. Using actors from Enterprise Ontology as organization building blocks for two large operationally merging airliners, experts systematically listed per actor (a) its organizational implementations, (b) its Quality of Business and (c) its IT implementations. The drafted DEMO Construction Model appeared to be the first neutral and shared language for describing the essence of the business. Also the results needed for decision making (a) were experienced as a necessary and sufficient validation of operational integrity and (b) were delivered fast, yielding a high Return On Modeling Effort.