ABO3 perovskites are of interest due to their large variety of electronic and magnetic properties. Under high pressure and high temperature conditions, we have recently found a new type of double double perovskite (DDPv) structure under high P-T conditions. Here CaMnCoReO6 and CaMnNiReO6 have been synthesized as new DDPv materials, with ferrimagnetic transitions (TC = 188 and 152 K) Neutron diffraction experiments are needed to determine further aspects of the crystal structures and the magnetic structures. Neutrons are needed to contrast Ca/Mn/Co(/Ni) order over 3 sites and accurate positions of oxygen anions in the structure will reveal the cation oxidation states via BVS calculations. The magnetic structures will enable Mn, Co or Ni, and Re site moments to be determined. 2 days on WISH are requested to collected data between 10 and 300 K.