A single-layer birefringent crystal trim retarder includes a birefringent crystal cut such that its optic axis is at a high oblique angle and such that it provides low in-plane retardance values even when the birefringent crystal is relatively thick. To compensate for the inherent high +C-plate retardance of this high-tilt O-plate, the single-layer birefringent crystal is coupled with a −C-plate thin-film retarder to provide a trim retarder having an overall A/−C-plate retarder functionality. This full-function trim retarder is practical to fabricate, is thickness and azimuthal angle tolerant, and is suitable for low sensitivity angular clocking requirements of LCoS panel compensation.