A corner stone in digital ergonomics is the positioning of digital human models into occupant configurations. Since seats play a major role for interiors, the human-seat interaction has to be considered for simulating postures. In most applications the classical H-Point model has been used. Since this approach is limited, the prediction has been refined by considering seat parameters like kinematics, upholstery surfaces and stiffness. But the necessity of stiffness parameters often hinders applying this method, since it requires extensive measurements based on a special indenter. To reduce this bottleneck, two improvements have been introduced. First, the measurement has been enhanced to be more generic and easier to perform. The process has been standardized in line with SAE J2896 and supports user-defined indenters. Second, an upholstery database has been implemented as alternative to measure the stiffness. The database is based on a sample of German vehicle seats and a statistical analysis of their measured force-deflection curves. A GUI supports the definition of characteristic curves. This can be done by selecting a referential curve, by setting individual parameters or by predicting a curve from the cushion stiffness. The final curves are suited for predicting the manikin or seat positions in interior designs.