Tactile sensors are composed of two substantial parts, the sensory structure and its cover. The characteristics of a sensor are fundamentally set by the sensor design, but are also essentially modified by the elastic cover on top. In this paper we analyze the pure mechanical information-coding effects of the sheltering rubber layer, applied on single-crystalline silicon 3D-force sensors, capable to detect both normal and shear forces. We give instructions on how to enhance the sensor's sensitivity by mimicking human tactile perception with introducing hair- and fingerprint-like elements to the sensor design.