Our recent neutron study showed that CaMnFeReO6 has a recently discovered ‘double double perovskite’ structure type with cations ordered across 3 distinct A-sites in columns while B-cations order in a rock-salt structure. To explore whether cation ordering across all five different crystallographic sites is possible we have synthesised two new materials which adopt this same structure type: CaMn0.5M0.5FeReO6 (M = Cu and Fe). Magnetisation data for CaMn0.5Cu0.5FeReO6 shows a high TC of 560 Kand a second A site spin ordering transition at 175 K. Two days of WISH beamtime are requested to establish crystallographic and magnetic structures. These materials are prepared by high pressure and temperature syntheses with a Walker-type multi-anvil module. Sample size is therefore limited and 60 mg polycrystalline samples will be used for data collection at a few temperatures between 10 and 300 K.