A modified Rice University‐type compact Mott spin polarimeter operating at 20 kV is adapted to a large commerical hemispherical electron energy analyzer. Normal energy analyzer functions are preserved via a retractable channeltron in the polarimeter acceleration column. In the spin‐detection mode, the polarimeter permits analysis of two orthogonal transverse spin‐polarization components. Electron trajectory analysis is used to optimize polarimeter lens column voltages in both normal and spin‐detection modes. Performance levels are established by experiments and significantly improved spin‐detection efficiency is shown to be accessible by changes in the polarimeter collection solid angle.