Recently we have carried out a comprehensive study of the crystal structure and magnetic order in SrFeO3-x [1] and Sr3Fe2O7-x [2,3]. In contrast to the magnetic phases of SrFeO3 and Sr8Fe8O23 we were not able to give a detailed description of the unknown magnetic structures of two phases labelled as V and VI. The present proposal is motivated by our very recent single crystal diffraction study on SrFeO2.813 and SrFeO2.834, carried out using the Flat-Cone-Diffractometer (E2), where we observed two sets of incommensurate magnetic reflections of the magnetic phases V and VI, which were unknown. In addition, a third incommensurate structure with the propagation vectors k = (0.16, 0.16, 0.16) was observed for SrFeO2.813 over the temperature range of 70 to 95 K. In this work, we propose to investigate two other single crystals SrFeO2.78 and SrFeO2.86 in continuation of our experiments on E2.