The purpose of this document is to investigate the feasibility of different detector layouts and geometries with respect to applications in coherent imaging at the SPB instrument of the European XFEL. Two detector designs, currently developed and implemented by the AGIPD and the DSSC consortia, are considered, with an emphasis on an accurate mathematical representation of the geometrical parameters, as far as they influence the experimental feasibility. Even though the two detectors are relatively different in design and only partially overlap in their applicable photon energy ranges, the general conclusions drawn here are very similar.