Academic interest in designing medical technology appropriate for Africa continues to grow, with funding available for innovations that answer complex questions. However, there is significant engineering work required to realise the promised impact of an innovation, even when it is shared as an Open Source design for others to build on. With academic innovation more highly prized by journals, funding bodies and academic institutions, this results in split priorities, and can lead to a difficult balance between the humanitarian aims of the project and pursuit of novel research. We present the OpenFlexure Microscope project as an example of an innovative academic project pushing the limits of 3D printed instrumentation. The microscope is already undergoing trials for malaria diagnosis, but significant product development is still necessary to transition the project from a prototype to a certified in-vitro diagnostic device. In this paper, we consider the engineering work that is needed to move from prototype to product, and how best to structure this work to support distributed manufacturing across Africa. We highlight the need to focus not just on the necessary engineering, but also on documenting this work so it can be understood and reproduced by any potential manufacturer.