A lapping tool assembly includes a mount tool and an interposer structure interposed between actuators and the mount tool, where the interposer includes interposer pins reactively coupled with the actuators such that each interposer pin is configured to receive a translational force from a corresponding actuator and to transmit the force to a corresponding actuation pin of the mount tool. The interposer may include a zero z-axis shift flexure system, and/or a z-axis decoupling flexure system, and/or alignment features, for accurately transmitting the actuation forces to the mount tool, while inhibiting affecting other portions of the mount tool.