Previous research on musical embodiment has reported that expert performers often regard their instruments as an extension of their body. Not every digital musical instrument seeks to create a close relationship between body and instrument, but even for the many that do, the design process often focuses heavily on technical and sonic factors, with relatively less attention to the bodily experience of the performer. In this paper we propose Somaesthetic design as an alternative to explore this space. The Soma method aims to attune the sensibilities of designers, as well as their experience of their body, and make use of these notions as a resource for creative design. We then report on a series of workshops exploring the relationship between the body and the guitar with a Soma design approach. The workshops resulted in a series of guitar-related artefacts and NIMEs that emerged from the somatic exploration of balance and tension during guitar performance. Lastly we present lessons learned from our research that could inform future Soma-based musical instrument design, and how NIME research may also inform Soma design.