The hepta-nuclear Fe(III) title compound Fe7 exhibits a unique antiferromagnetic exchange topology reminiscent of a three-bladed propeller, giving rise to spin frustration, also suggested by the observed unprecedented Mössbauer spectra. However, both the magnetic and Mössbauer responses could not yet be explained beyond simplistic phenomenological models. We here suggest to study the low-energy spin excitations in Fe7 by inelastic neutron scattering to facilitate a proper magnetic modelling of the system. From numerical simulations and fits to the magnetization curves we expect a spin transition at ca. 0.8 meV and a further spin transition in the range of 0.3 to 2 meV, which we want to observe in this experiment. The IRIS spectrometer is very well suited for this energy range.