A load detecting vehicle seat assembly includes a discrete strain gage mounting plate having a specified flatness to produce desired strain gage performance. The strain gage mounting plate is disposed between a strain gage and a vehicle seat component, such as a cushion frame, so that vehicle seat loading is transferred to the strain gage through the mounting plate. The strain gage may be mounted with a central portion secured to a lower vehicle seat component and outward portions secured to an upper vehicle seat component such that only the outward portions of the strain gage contact the strain gage mounting plate, which has a controlled flatness tolerance to produce desired strain gage performance.