The family of guanidinium metal formates has the perovskite structure and, like many perovskites, is of interest for these materials' magnetic and electric properties, in particular the possibility of multiferroicity. The phase diagrams of these compounds, however, remain largely unexplored. We have recently (RB1410586) collected PEARL data demonstrating that both the cobalt and the manganese compounds have high-pressure rhombohedral phases. Unfortunately, we lost substantial amounts of beam time both in the original experiment and in replacement time, and thus collected relatively little data on these new phases. We therefore propose to collect data at more pressure and temperature points to enable a full investigation of the structural changes associated with this phase transition, in particular the relative distortions of the coordination polyhedra and framework structure.