The metal-organic Prussian blue analogues (HIm)2K[M(CN)6], where HIm is the imidazolium cation and M = Fe or Co, have switchable dielectric constants, since the imidazolium ions are free to rotate in their planes at high T but freeze into a single orientation at low T. Both materials exhibit an intermediate-T phase isosymmetric to the high-T phase; the nature of this phase is not obvious, but analysis of the spontaneous strain associated with both phase transitions suggests important differences between the Fe and Co compounds related to the differences in cation size. However, this analysis is based on few measurements of limited precision. We propose here an HRPD study in order to measure the spontaneous strain at many temperature points and to high precision, to resolve the differences between these materials and direct future work on electrically functional framework materials.