System maps are established tools in design practice and education as well as non-design research, both as a process and an outcome of systemic analysis and synthesis. Applying causal loop diagrams (CLD's) in (systemic) design research could be of great value to tackle the growing societal complexity. At this moment there is, however, no clear research protocol to include the rich data necessary for systemic research and ensure a scientifically valid system map in the context of design research. In this paper, we propose a protocol using CLD's as a research method and outcome in design-inclusive research. The protocol synthesises rich data from qualitative research in a way that the representation yields higher validity compared to the regular approach to systems mapping, using a process of reflection and iteration on boundary setting. An iterative process of qualitative research methods with lean validation methods was used to come to a conceptual proposal. The protocol can support systemic design researchers and practitioners to include a scientifically grounded CLD in the explorative research actions phase, thus bridging the research towards a phase of creative design actions.